Medical Laboratory Science Review- Harr - Immunology

From the following, identify a specific component of the adaptive immune system that is formed in response to antigenic stimulation:

A. Lysozyme

B. Complement

C. Commensal organisms

D. Immunoglobulin

D. Immunoglobulin is a specific part of the adaptive immune system and is formed only in response to a specific antigenic stimulation. Complement, lysozyme, and commensal organisms all act nonspecifically as a part of the adaptive immune system. These three components do not require any type of specific antigenic stimulation.

Which two organs are considered the primary lymphoid organs in which immunocompetent cells originate and mature?

A. Thyroid and Peyer's Patch

B. Thymus and bone marrow

C. Spleen and mucosal-associated lymphoid tissue (MALT)

D. Lymph nodes and thoracic duct

B. The bone marrow and thymus are considered primary lymphoid organs because immunocompetent cells either originate or mature in them. Some immunocompetent cells mature or reside in the bone marrow (the source of all hematopoietic cells) until transported to the thymus, spleen, or Peyer's patches, where they process antigen or manufacture antibody. T lymphocytes, after originating in the bone marrow, travel to the thymus to mature and differentiate.

What type of B cells are formed after antigen stimulation?

A. Plasma cells and memory B cells

B. Mature B cells

C. Antigen-dependent B cells

D. Receptor-activated B cells

A. Mature B cells exhibit surface immunoglobulin that may cross link a foreign antigen, thus forming the activated B cell and leading to capping and internalization of antigen. The activated B cell gives rise to plasma cells that produce and secrete immunoglobulins and memory cells that reside in lymphoid organs.

T cells travel from the bone marrow to the thymus for maturation. What is the correct order of the maturation sequence for T cells in the thymus?

A. Bone marrow to the cortex; after thymic education, released back to peripheral circulation

B. Maturation and selection occur in the cortex; migration to the medulla; release of mature T cells to secondary lymphoid organs

C. Storage in either the cortex or medulla; release of T cells into the peripheral circulation

D. Activation and selection occur in the medulla; mature T cells are stored in the cortex until activated by antigen

B. Immature T cells travel from the bone marrow to the thymus to mature into functional T cells. Once in the thymus, T cells undergo a selection and maturation sequence that begins in the cortex and moves to the medulla of the thymus. Thymic factors such as thymosin and thymopoietin and cells within the thymus such as macrophages and dendritic cells assist in this sequence. After completion of the maturation cycle, T cells are released to secondary lymphoid organs to await antigen recognition and activation.

Which cluster of differentiation (CD) marker appears during the first stage of T-cell development and remains present as an identifying marker for T cells?

A. CD 1

B. CD 2

C. CD 3

D. CD 4 or CD 8

B. the CD 2 marker appears during the first stage of T-cell development and can be used to differentiate T cells from other lymphocytes. This T-lymphocyte receptor binds sheep red blood cells (RBCs). This peculiar characteristic was the basis for the classic E rosette test once used to enumerate T cells in peripheral blood. CD2 is not specific for T cells, however, and is also found on large granular lymphocytes (LGL or natural killer [NK]cells).

Which markers are found on mature, peripheral helper T cells?

A. CD 1, CD 2, CD 4

B. CD 2, CD 3, CD 8

C. CD 1, CD 3, CD 4

D. CD 2, CD 3, CD 4

D. Mature. peripheral helper T cells have the CD 2 (E rosette), CD 3 (mature T cell), and CE 4 (helper) markers.

Which T cell expresses the CD8 marker and acts specifically to kill tumor or virally infected cells?

A. Helper T

B. T suppressor

C. T cytotoxic

D. T inducer/suppressor

C. T cytotoxic cells recognize antigen in association with major histocompatibility complex (MHC) class I complexes and act against target cells that express foreign antigens. These include viral antigens and the human leukocyte antigens (HLA) that are the target of graft rejection.

How are cytotoxic T cells (Tc cells) and natural killer (NK) cells similar?

A. Require antibody to be present

B. Effective against virally infected cells

C. Recognize antigen in association with HLA class II markers

D. Do not bind to infected cells

B Both TC and NK cells are effective against virally

infected cells, and neither requires antibody to be

present to bind to infected cells. NK cells do not

exhibit MHC class restriction, whereas activation of

Tc cells require the presence of MHC class I

molecules in association with the viral antigen.

What is the name of the process by which phagocytic cells are attracted to a substance such as a bacterial peptide?

A. Diapedesis

B. Degranulation

C. Chemotaxis

D. Pahotaxis

C Chemotaxis is the process by which phagocytic cells are attracted toward an area where they detect a disturbance in the normal functions of body tissues. Products from bacteria and viruses, complement components, coagulation proteins, and cytokines from other immune cells may all act as chemotactic factors.

All of the following are immunologic functions of complement except:

A. Induction of an antiviral state

B. Opsonization

C. Chemotaxis

D. Anaphylatoxin formation

A Complement components are serum proteins that function in opsonization, chemotaxis, and anaphylatoxin formation but do not induce an antiviral state in target cells. This function is performed by interferons.

Which complement component is found in both the classic and alternative pathways?

A. C1

B. C4

C. Factor D

D. C3

D. C3 is found in both the classic and alternative (alternate) pathways of the complement system. In the classic pathway, C3b forms a complex on the cell with C4b2a that enzymatically cleaves C5. In the alternative pathway, C3b binds to an activator on the cell surface. It forms a complex with factor B called C3bBb which , like C4b2a3b, can split C5.

Which immunoglobulin(s) help(s) initiate the classic complement pathway?

A. IgA and IgD

B. IgM only

C. IgG and IgM

D. IgG only

C Both IgG and IgM are the immunoglobulins that help to initiate the activation of the classic complement pathway. IgM is a more potent complement activator, however.

How is complement activity destroyed in vitro?

A. Heating serum at 56oC for 30 min

B. Keeping serum at room temperature of 22oC for 1 hour

C. Heating serum at 37oC for 45 min

D. Freezing serum at 0oC for 24 hours

A complement activity in serum in vitro is destroyed by heating the serum at 56oC fir 30 min. In test procedures where complement may interfere with the test system, it may be necessary to destroy complement activity in the test sample by heat inactivation.

What is the purpose of C3a, C4a, and C5a, the

split products of the complement cascade?

A. To bind with specific membrane receptors of

lymphocytes and cause release of cytotoxic

substances

B. To cause increased vascular permeability,

contraction of smooth muscle, and release of

histamine from basophils

C. To bind with membrane receptors of

macrophages to facilitate phagocytosis and the

removal of debris and foreign substances

D. To regulate and degrade membrane cofactor

protein after activation by C3 convertase

B C3a, C4a, and C5a are split products of the

complement cascade that participate in various

biological functions such as vasodilation and smooth muscles contraction. Theses small pepetides act as anaphylatoxins, e.g., effector molecules that participate in the inflammatory response to assist in the destruction and clearance of foreign antigens.

Which region of the immunoglobulin molecule

can bind antigen?

A. Fab

B. Fc

C. CL

D. CH

A The Fab (fragment antigen binding) is the region of the immunoglobulin molecule that can bind antigen. Two Fab fragments are formed from hydrolysis of the immunoglobulin molecule by papain. Each consists of a light chain and the VH and CH1 regions of the heavy chain. The variable regions of the light and heavy chains interact, forming a specific antigen-combining site.

Which region determines whether an

immunoglobulin molecule can fix

complement?

A. VH

B. CH

C. VL

D. CL

B The composition and structure of the constant

region of the heavy chain determine whether that

immunoglobulin will fix complement. The Fc

fragment (fragment crystallizable) is formed by partial immunoglobulin digestion with papain and includes the CH2 and CH3 domains of both heavy chains. The complement component C1q molecule will bind to the CH2 region of an IgG or IgM molecule.

Which immunoglobulin class(es) has (have) a

J chain?

A. IgM

B. IgE and IgD

C. IgM and sIgA

D. IgG3 and IgA

C Both IgM and secretory IgA have a J chain joining individual molecules together; the J chain in IgM joins five molecules and the J chain in sIgA joins two molecules.

Which immunoglobulin appears first in the

primary immune response?

A. IgG

B. IgM

C. IgA

D. IgE

characteristics/Immunoglobulins/Functions/1

B The first antibody to appear in the primary immune response to an antigen is IgM. The titer of antiviral IgM (e.g., IgM antibody to cytomegalovirus [anti-CMV]) is more specific for acute or active viral infection than IgG and may be measured to help differentiate active from prior infection.

Which immunoglobulin appears in highest titer in

the secondary response?

A. IgG

B. IgM

C. IgA

D. IgE

A A high titer of IgG characterizes the secondary

immune response. Consequently, IgG antibodies

comprise about 80% of the total immunoglobulin

concentration in normal serum.

Which immunoglobulin can cross the placenta?

A. IgG

B. IgM

C. IgA

D. IgE

A IgG is the only immunoglobulin class that can cross the placenta. All subclasses of IgG can cross the placenta, but IgG2 crosses more slowly. This process requires recognition of the Fc region of the IgG by placental cells. These cells take up the IgG from the maternal blood and secrete it into the fetal blood, providing humoral immunity to the neonate for the first few months after delivery

Which immunoglobulin cross links mast cells to

release histamine?

A. IgG

B. IgM

C. IgA

D. IgE

D IgE is the immunoglobulin that cross links with

basophils and mast cells. IgE causes the release of

such immune response modifiers as histamine and

mediates an allergic immune response

All of the following are functions of

immunoglobulins except:

A. Neutralizing toxic substances

B. Facilitating phagocytosis through opsonization

C. Interacting with TC cells to lyse viruses

D. Combining with complement to destroy cellular

antigens

C Cytotoxic T cells lyse virally infected cells directly, without requirement for specific antibody. The TC cell is activated by viral antigen that is associated with MHC class I molecules on the surface of the infected cell. The activated TC cell secretes several toxins, such as tumor necrosis factor, which destroy the infected

cell and virions.

Which of the following cell surface molecules is

classified as an MHC class II antigen?

A. HLA-A

B. HLA-B

C. HLA-C

D. HLA-DR

D The MHC region is located on the short arm of

chromosome 6 and codes for antigens expressed

on the surface of leukocytes and tissues. The MHC

region genes control immune recognition; their

products include the antigens that determine

transplantation rejection. HLA-DR antigens are

expressed on B cells. HLA-DR2, DR3, DR4, and DR5 antigens show linkage with a wide range of

autoimmune diseases.

Which MHC class of molecule is necessary for

antigen recognition by CD4-positive T cells?

A. Class I

B. Class II

C. Class III

D. No MHC molecule is necessary for antigen

recognition

B Helper T lymphocytes (CD4-positive T cells)

recognize antigens only in the context of a class II

molecule. Because class II antigens are expressed on macrophages, monocytes, and B cells, the helper T-cell response is mediated by interaction with processed antigen on the surface of these cells.

Which of the following are products of HLA

class III genes?

A. T-cell immune receptors

B. HLA-D antigens on immune cells

C. Complement proteins C2, C4, and Factor B

D. Immunoglobulin VL regions

C Complement components C2 and C4 of the classic pathway and Factor B of the alternative pathway are class III molecules. HLA-A, HLA-B, and HLA-C antigens are classified as class I antigens, and HLA-D, HLA-DR, HLA-DQ, and HLA-DP antigens as class II antigens.

What molecule on the surface of most T cells

recognizes antigen?

A. IgT, a four-chain molecule that includes the tau

heavy chain

B. MHC protein, a two-chain molecule encoded by

the HLA region

C. CD3, consisting of six different chains

D. TcR, consisting of two chains, alpha and beta

D T cells have a membrane bound receptor (T-cell

receptor or TcR) that is antigen specific. This two-

chain molecule consists of a single α-chain, similar to an immunoglobulin light chain, and a single β-chain, similar to an immunoglobulin heavy chain. Some T cells may express a γ-δ receptor instead of the α-β molecule. There is no τ heavy chain. MHC and CD3 molecules are present on T cells, but they are not the molecules that give antigen specificity to the cell.

The T-cell antigen receptor is similar to

immunoglobulin molecules in that it:

A. Remains bound to the cell surface and is never

secreted

B. Contains V and C regions on each of its chains

C. Binds complement

D. Can cross the placenta and provide protection to

a fetus

B The antigen binding regions of both the α- and

β-chains of the T-cell receptor are encoded by

V genes that undergo rearrangement similar to that observed in immunoglobulin genes. The α-chain gene consists of V and J segments, similar to an immunoglobulin light chain. The β-chain consists of V, D, and J segments, similar to an immunoglobulin heavy chain. The α- and β-chains each have a single C-region gene encoding the constant region of the molecule. While answer A is true for T-cell receptors, it is not true for immunoglobulins that can be cell bound or secreted. Answers C and D are true for

certain immunoglobulin heavy-chain isotypes but

are not true for the T-cell receptor.

Toll-like receptors are found on which cells?

A. T cells

B. Dendritic cells

C. B cells

D. Large granular lymphocytes

B Toll-like receptors (TLR) are the primary antigen

recognition protein of the innate immune system.

They are found on antigen-presenting cells such as dendritic cells and macrophages. Eleven TLRs have been described. TLRs recognize certain structural motifs common to infecting organisms. TLR 4, for example, recognizes bacterial lipopolysaccharide (LPS). The name comes from their similarity to the Toll protein in Drosophila.

Macrophages produce which of the following

proteins during antigen processing?

A. IL-1 and IL-6

B. γ-Interferon

C. IL-4, IL-5, and IL-10

D. Complement components C1 and C3

A Interleukin-1 (IL-1) and IL-6 are proinflammatory

macrophage-produced cytokines. In addition to their inflammatory properties, they activate T-helper cells during antigen presentation. γ-Interferon, IL-4, 5, and 10 are all produced by T cells. Complement components are produced by a variety of cells but are not part of the macrophage antigen presentation process.

A superantigen, such as toxic shock syndrome

toxin-1 (TSST-1), bypasses the normal antigen

processing stage by binding to and cross linking:

A. A portion of an immunoglobulin molecule and

complement component C1

B. Toll-like receptors and an MHC class 1 molecule

C. A portion of an immunoglobulin and a portion

of a T-cell receptor

D. A portion of a T-cell receptor and an MHC

class II molecule

D A superantigen binds to the V β portion of the T-cell receptor and an MHC class II molecule. This binding can activate T cells without the involvement of an antigen-presenting cell. In some individuals, a single V β protein that recognizes TSST-1 is expressed on up to 10%-20% of T cells. The simultaneous activation of this amount of T cells causes a heavy cytokine release, resulting in the vascular collapse and pathology of toxic shock syndrome.

T regulator cells, responsible for controlling

autoimmune antibody production, express which

of the following phenotypes?

A. CD3, CD4, CD8

B. CD3, CD8, CD25

C. CD3, CD4, CD25

D. CD8, CD25, CD56

C T regulator cells are believed to be the primary

immune suppressor cells and express CD3, CD4, and CD25. CD25 is the interleukin 2 receptor. CD25 may be expressed by activated T cells, but is constitutively expressed by the T-regulator cells. CD25 expression on T-regulator cells occurs in the thymus and is regulated by the FOXP3 protein.

The interaction between an individual antigen

and antibody molecule depends upon several

types of bonds such as ionic bonds, hydrogen

bonds, hydrophobic bonds, and van der Waals

forces. How is the strength of this attraction

characterized?

A. Avidity

B. Affinity

C. Reactivity

D. Valency

B Affinity refers to the strength of a single antibody- antigen interaction. Avidity is the strength of interactions between many different antibodies in a serum against a particular antigen (i.e., the sum of many affinities).

A laboratory is evaluating an enzyme-linked

immunosorbent assay (ELISA) for detecting an

antibody to cyclic citrullinated peptide (CCP),

which is a marker for rheumatoid arthritis. The

laboratory includes serum from healthy volunteers

and patients with other connective tissue diseases

in the evaluation. These specimens determine

which factor of the assay?

A. Sensitivity

B. Precision

C. Bias

D. Specificity

D Specificity is defined as a negative result in the

absence of the disease. The non-rheumatoid

arthritis specimens would be expected to test

negative if the assay has high specificity. Precision

is the ability of the assay to repeatedly yield the

same results on a single specimen. Both bias and

sensitivity calculations would include specimens

from rheumatoid arthritis specimens. Although

those specimens would be included in the

evaluation, they are not listed in the question

The detection of precipitation reactions depends

on the presence of optimal proportions of antigen

and antibody. A patient's sample contains a large

amount of antibody, but the reaction in a test system

containing antigen is negative. What has happened?

A. Performance error

B. Low specificity

C. A shift in the zone of equivalence

D. Prozone phenomenon

D Although performance error and low specificity

should be considered, if a test system fails to yield

the expected reaction, excessive antibody

preventing a precipitation reaction is usually the

cause. Prozone occurs when antibody molecules

saturate the antigen sites, preventing cross linking

of the antigen-antibody complexes by other

antibody molecules. Because the antigen and

antibody do not react at equivalence, a visible

product is not formed, leading to a false-negative

result.

Which part of the radial immunodiffusion (RID)

test system contains the antisera?

A. Center well

B. Outer wells

C. Gel

D. Antisera may be added to any well

C In an RID test system, for example, one measuring hemopexin concentration, the gel would contain the antihemopexin. A standardized volume of serum containing the antigen is added to each well. Antigen diffuses from the well into the gel and forms a precipitin ring by reaction with antibody. At equivalence, the area of the ring is proportional to antigen concentration.

What is the interpretation when an Ouchterlony

plate shows crossed lines between wells 1 and 2

(antigen is placed in the center well and antisera in

wells 1 and 2)?

A. No reaction between wells 1 and 2

B. Partial identity between wells 1 and 2

C. Nonidentity between wells 1 and 2

D. Identity between wells 1 and 2

C Crossed lines indicate nonidentity between

wells 1 and 2. The antibody from well 1 recognizes

a different antigenic determinant than the antibody

from well 2.

Why is a chemiluminescent immunoassay (CIA) or

enzyme immunoassay (EIA) the method of choice

for detection of certain analytes, such as hormones,

normally found in low concentrations?

A. Because of low cross reactivity

B. Because of high specificity

C. Because of high sensitivity

D. Because test systems may be designed as both

competitive and noncompetitive assays

C The sensitivity of EIA methods producing visible

color change, and fluorescent and chemiluminescent products approaches nanogram levels of antibody. These methods are easily automated.

What comprises the indicator system in an indirect

ELISA for detecting antibody?

A. Enzyme-conjugated antibody + chromogenic

substrate

B. Enzyme conjugated antigen + chromogenic

substrate

C. Enzyme + antigen

D. Substrate + antigen

A The ELISA test measures antibody using immobilized reagent antigen. The antigen is fixed to the walls of a tube or bottom of a microtiter well. Serum is added (and incubated) and the antibody binds, if present. After washing, the antigen-antibody complexes are detected by adding an enzyme labeled anti-immunoglobulin. The unbound enzyme label is removed by washing, and the bound enzyme label is detected by adding chromogenic substrate. The enzyme catalyzes the conversion of substrate to colored product.

What outcome results from improper washing of a

tube or well after adding the enzyme-antibody

conjugate in an ELISA system?

A. Result will be falsely decreased

B. Result will be falsely increased

C. Result will be unaffected

D. Result is impossible to determine

B If unbound enzyme-conjugated anti-immunoglobulin is not washed away, it will catalyze conversion of substrate to colored product, yielding a falsely elevated result.

What would happen if the color reaction phase is

prolonged in one tube or well of an ELISA test?

A. Result will be falsely decreased

B. Result will be falsely increased

C. Result will be unaffected

D. Impossible to determine

B If the color reaction is not stopped within the time limits specified by the procedure, the enzyme will continue to act on the substrate, producing a falsely elevated test result.

The absorbance of a sample measured by ELISA is

greater than the highest standard. What corrective

action should be taken?

A. Extrapolate an estimated value from the highest

reading

B. Repeat the test using a standard of higher

concentration

C. Repeat the assay using one half the volume of the

sample

D. Dilute the test sample

D Usually when a test sample reads at a value above

the highest standard in an ELISA test, it is diluted

and measured again. In those instances where no

additional clinical value can be obtained by dilution,

the result may be reported as greater than the

highest standard (citing the upper reportable limit

of the assay).

A patient was suspected of having a

lymphoproliferative disorder. After several

laboratory tests were completed, the patient was

found to have an IgMκ paraprotein. In what

sequence should the laboratory tests leading to

this diagnosis have been performed?

A. Serum protein electrophoresis (SPE) followed

by immunofixation electrophoresis (IFE)

B. Immunoglobulin levels followed by SPE

C. Total lymphocyte count followed by

immunoglobulin levels

D. Immunoglobulin levels followed by urine protein

electrophoresis

A Serum protein electrophoresis should be performed initially to detect the presence of an abnormal immunoglobulin that demonstrates restricted electrophoretic mobility. A patient producing only monoclonal light chains may not show any abnormal serum finding because the light chains may be excreted in the urine. A positive finding for either serum or urine should be followed by IFE on the positive specimen. This is required to confirm the presence of monoclonal immunoglobulin and to identify the heavy and light chain type.

An IFE performed on a serum sample showed a

narrow dark band in the lanes containing anti-γ

and anti-λ. How should this result be interpreted?

A. Abnormally decreased IgG concentration

B. Abnormal test result demonstrating monoclonal

IgGλ

C. Normal test result

D. Impossible to determine without densitometric

quantitation

B A narrow dark band formed in both the lane

containing anti-γ and anti-λ indicates the

presence of a monoclonal IgG λ immunoglobulin.

A diffuse dark band would indicate a polyclonal

increase in IgG that often accompanies chronic

inflammatory disorders such as systemic lupus

erythematosus (SLE).

Which type of nephelometry is used to measure

immune complex formation almost immediately

after reagent has been added?

A. Rate

B. Endpoint

C. Continuous

D. One dimensional

A Rate nephelometry is used to measure formation of small immune complexes as they are formed under conditions of antibody excess. The rate of increase in photodetector output is measured within seconds or minutes and increases with increasing antigen concentration. Antigen concentration is determined by comparing the rate for the sample to that for standards using an algorithm that compensates for nonlinearity. In endpoint nephelometry, reactions are read after equivalence. Immune complexes are of maximal size but may have a tendency to settle out of solution, thereby decreasing the amount of scatter.

An immunofluorescence microscopy assay (IFA)

was performed, and a significant antibody titer was

reported. Positive and negative controls performed

as expected. However, the clinical evaluation of the

patient was not consistent with a positive finding.

What is the most likely explanation of this

situation?

A. The clinical condition of the patient changed

since the sample was tested

B. The pattern of fluorescence was misinterpreted

C. The control results were misinterpreted

D. The wrong cell line was used for the test

B In an IFA, for example, an antinuclear antibody

(ANA) test, the fluorescence pattern must be

correlated correctly with the specificity of the

antibodies. Both pathological and nonpathological

antibodies can occur, and antibodies may be

detected at a significant titer in a patient whose

disease is inactive. Failure to correctly identify

subcellular structures may result in misinterpretation of the antibody specificity, or a false positive caused by nonspecific fluorescence.

What corrective action should be taken when an

indeterminate pattern occurs in an indirect IFA?

A. Repeat the test using a larger volume of sample

B. Call the physician

C. Have another medical laboratory scientist read

the slide

D. Dilute the sample and retest

D An unexpected pattern may indicate the presence of more than one antibody. Diluting the sample may help to clearly show the antibody specificities, if they are found in different titers. If the pattern is still atypical, a new sample should be collected and the test repeated.

Which statement best describes passive

agglutination reactions used for serodiagnosis?

A. Such agglutination reactions are more rapid

because they are a single-step process

B. Reactions require the addition of a second

antibody

C. Passive agglutination reactions require biphasic

incubation

D. Carrier particles for antigen such as latex particles

are used

D Most agglutination tests used in serology employ passive or indirect agglutination where carrier particles are coated with the antigen. The carrier molecule is of sufficient size so that the reaction of the antigen with antibody results in formation of a complex that is more easily visible.

What has happened in a titer, if tube Nos. 5-7

show a stronger reaction than tube Nos.1-4?

A. Prozone reaction

B. Postzone reaction

C. Equivalence reaction

D. Poor technique

A In tubes Nos.1-4, insufficient antigen is present to give a visible reaction because excess antibody has saturated all available antigen sites. After dilution of antibody, tubes Nos.1-4 have the equivalent concentrations of antigen and antibody to allow formation of visible complexes.

What is the titer in tube No. 8 if tube No. 1 is

undiluted and dilutions are doubled?

A. 64

B. 128

C. 256

D. 512

B The antibody titer is reciprocal of the highest dilution of serum giving a positive reaction. For doubling dilutions, each tube has one half the amount of serum as the previous tube. Because the first tube was undiluted (neat), the dilution in tube No. 8 is (1/2)7 and the titer equals 27 or 128.

The directions for a slide agglutination test

instruct that after mixing the patient's serum

and latex particles, the slide must be rotated for

2 minutes. What would happen if the slide were

rotated for 10 minutes?

A. Possible false-positive result

B. Possible false-negative result

C. No effect

D. Depends on the amount of antibody present in

the sample

A Failure to follow directions, as in this case where

the reaction was allowed to proceed beyond the

recommended time, may result in a false-positive

reading. Drying on the slide may lead to a possible erroneous positive reading.

Which outcome indicates a negative result in a

complement fixation test?

A. Hemagglutination

B. Absence of hemagglutination

C. Hemolysis

D. Absence of hemolysis

C In complement fixation, hemolysis indicates a

negative test result. The absence of hemolysis

indicates that complement was fixed in an

antigen-antibody reaction and, therefore, that the

specific complement binding antibody was present in the patient's serum. Consequently, it was not available to react in the indicator system.

What effect does selecting the wrong gate have

on the results when cells are counted by flow

cytometry?

A. No effect

B. Failure to count the desired cell population

C. Falsely elevated results

D. Impossible to determine

B Gating is the step performed to select the proper cells to be counted. Failure to properly perform this procedure will result in problems in isolating and counting the desired cells. It is impossible to determine if the final result would be falsely elevated or falsely lowered by problems with gating.

Which statement best describes

immunophenotyping?

A. Lineage determination by detecting antigens on

the surface of the gated cells using fluorescent

antibodies

B. Identification of cell maturity using antibodies to

detect antigens within the nucleus

C. Identification and sorting of cells by front and

side-scatter of light from a laser

D. Analysis of cells collected by flow cytometry

using traditional agglutination reactions

A Immunophenotyping refers to classification of cells (lineage and maturity assignment) using a panel of fluorescent-labeled antibodies directed against specific surface antigens on the cells. Antibodies are referred to by their CD (cluster of differentiation) number. Monoclonal antibodies having a common CD number do not necessarily bind to the same epitope but recognize the same antigen on the cell surface. Reactivity of the selected cells with a panel of antibodies differentiates lymphoid from myeloid cells

and identifies the stage of cell maturation.

A flow cytometry scattergram of a bone marrow

sample shows a dense population of cells located

in-between normal lymphoid and normal myeloid

cells. What is the most likely explanation?

A. The sample was improperly collected

B. An abnormal cell population is present

C. The laser optics are out of alignment

D. The cells are most likely not leukocytes

B Lymphoid cells and myeloid cells display in

predictable regions of the scatterplot because of their characteristic size and density. Lymphoid cells cause less forward and side scatter from the laser than do myeloid cells. A dense zone of cells in between those regions is caused by the presence of a large number of abnormal cells, usually blasts. The lineage of the cells can be determined by immunophenotyping with a panel of fluorescent-labeled antibodies.

Which serum antibody response usually

characterizes the primary (early) stage of syphilis?

A. Antibodies against syphilis are undetectable

B. Detected 1-3 weeks after appearance of the

primary chancre

C. Detected in 50% of cases before the primary

chancre disappears

D. Detected within 2 weeks after infection

B During the primary stage of syphilis, about 90% of patients develop antibodies between 1 and 3 weeks after the appearance of the primary chancre.

What substance is detected by the rapid plasma

reagin (RPR) and Venereal Disease Research

Laboratory (VDRL) tests for syphilis?

A. Cardiolipin

B. Anticardiolipin antibody

C. Anti-T. pallidum antibody

D. Treponema pallidum

B Reagin is the name for a nontreponemal antibody that appears in the serum of syphilis-infected persons and is detected by the RPR and VDRL assays. Reagin reacts with cardiolipin, a lipid-rich extract of beef heart and other animal tissues.

What type of antigen is used in the RPR card test?

A. Live treponemal organisms

B. Killed suspension of treponemal organisms

C. Cardiolipin

D. Tanned sheep cells

C Cardiolipin is extracted from animal tissues, such as beef hearts, and attached to carbon particles. In the presence of reagin, the particles will agglutinate.

Which of the following is the most sensitive test to

detect congenital syphilis?

A. VDRL

B. RPR

C. Microhemagglutinin test for T. pallidum

(MHA-TP)

D. Polymerase chain reaction (PCR)

D The PCR will amplify a very small amount of DNA from T. pallidum and allow for detection of the organism in the infant. Antibody tests such as VDRL and RPR may detect maternal antibody only, not indicating if the infant has been infected.

A biological false-positive reaction is least likely

with which test for syphilis?

A. VDRL

B. Fluorescent T. pallidum antibody absorption test

(FTA-ABS)

C. RPR

D. All are equally likely to detect a false-positive

result

B The FTA-ABS test is more specific for T. pallidum

than nontreponemal tests such as the VDRL and RPR and would be least likely to detect a

biological false-positive result. The FTA-ABS test

uses heat-inactivated serum that has been absorbed with the Reiter strain of T. pallidum to remove nonspecific antibodies. Nontreponemal tests have a biological false-positive rate of 1%-10%, depending upon the patient population tested. False-positive findings are caused commonly by infectious mononucleosis (IM), SLE, viral hepatitis, and human immunodeficiency virus (HIV) infection.

A 12-year old girl has symptoms of fatigue and a

localized lymphadenopathy. Laboratory tests reveal

a peripheral blood lymphocytosis, a positive RPR,

and a positive spot test for IM. What test should

be performed next?

A. HIV test by ELISA

B. VDRL

C. Epstein-Barr virus (EBV) specific antigen test

D. Treponema pallidum particle agglutination

(TP-PA) test

D The patient's symptoms are nonspecific and could be attributed to many potential causes. However, the patient's age, lymphocytosis, and serological results point to infectious mononucleosis (IM). The rapid spot test for antibodies seen in IM is highly specific. The EBV-specific antigen test is more sensitive but is unnecessary when the spot test is positive. HIV infection is uncommon at this age and is often associated with generalized lymphadenopathy

and a normal or reduced total lymphocyte count. IM antibodies are commonly implicated as a cause of biological false-positive nontreponemal tests for syphilis. Therefore, a treponemal test for syphilis should be performed to document this phenomenon in this case.

Which test is most likely to be positive in the

tertiary stage of syphilis?

A. FTA-ABS

B. RPR

C. VDRL

D. Reagin screen test (RST)

A The FTA-ABS or one of the treponemal tests is more likely to be positive than a nontreponemal test in the tertiary stage of syphilis. In some cases, systemic lesions have subsided by the tertiary stage and the nontreponemal tests become seronegative. Although the FTA-ABS is the most sensitive test for tertiary syphilis, it will be positive in both treated and untreated cases.

What is the most likely interpretation of the

following syphilis serological results?

RPR: reactive; VDRL: reactive; MHA-TP: nonreactive

A. Neurosyphilis

B. Secondary syphilis

C. Syphilis that has been successfully treated

D. Biological false positive

D A positive reaction with nontreponemal antigen and a negative reaction with a treponemal antigen is most likely caused by a biological false-positive nontreponemal test.

Which specimen is the sample of choice to

evaluate latent or tertiary syphilis?

A. Serum sample

B. Chancre fluid

C. CSF

D. Joint fluid

C Latent syphilis usually begins after the second year of untreated infection. In some cases, the serological tests become negative. However, if neurosyphilis is present, cerebrospinal fluid serology will be positive and the CSF will display increased protein and pleocytosis characteristic of central nervous system infection.

Interpret the following quantitative RPR test results. RPR titer: weakly reactive 1:8; reactive 1:8-1:64

A. Excess antibody, prozone effect

B. Excess antigen, postzone effect

C. Equivalence of antigen and antibody

D. Impossible to interpret; testing error

A This patient may be in the secondary stage of syphilis and is producing large amounts of antibody to T. pallidum sufficient to cause antibody excess in the test. The test became strongly reactive only after the antibody was diluted

Tests to identify infection with HIV fall into which three general classification types of tests?

A. Tissue culture, antigen, and antibody tests

B. Tests for antigens, antibodies, and nucleic acid

C. DNA probe, DNA amplification, and Western blot tests

D. ELISA, Western blot, and Southern blot tests

B Two common methods for detecting antibodies to HIV are the ELISA and Western blot tests. Two common methods for detecting HIV antigens are ELISA and immunofluorescence. Two common methods for detecting HIV genes are the Southern blot test and DNA amplification using the polymerase chain reaction to detect viral nucleic acid in infected lymphocytes.

Which tests are considered screening tests for HIV?

A. ELISA, 4th generation, and rapid antibody tests

B. Immunofluorescence, Western blot,

radioimmuno-precipitation assay

C. Culture, antigen capture assay, DNA

amplification

D. Reverse transcriptase and messenger RNA (mRNA) assay

A ELISA, rapid antibody tests, as well as the 4th generation automated antigen/antibody combination assays are screening tests for HIV. The 4th generation assays detect both antigen and antibody.

Which tests are considered confirmatory tests for HIV?

A. ELISA and rapid antibody tests

B. Western blot test, HIC-1,2 differentiation assays, and polymerase chain reaction

C. Culture, antigen capture assay, polymerase chain reaction

D. Reverse transcriptase and mRNA assay

B Western blot, and PCR tests are generally used as confirmatory tests for HIV. An HIV-1,2 differentiation assay is recommended as the confirming procedure following a reactive 4th generation HIV assay. PCR, however, is more often used for early detection of HIV infection, for documenting infant HIV infection, and for following antiviral therapy.

Which is most likely a positive Western blot result for infection with HIV?

A. Band at p24

B. Band at gp60

C. Bands at p24 and p31

D. Bands at p24 and gp120

D To be considered positive by Western blot testing, bands must be found for at least two of the following three HIV proteins: gp41, p24, and gp120 or 160. The p24 band denotes antibody to a gag protein. The gp160 is the precursor protein from which gp120 and gp41 are made; these are env proteins.

A woman who has had five pregnancies

subsequently tests positive for HIV by Western blot. What is the most likely reason for this result?

A. Possible cross-reaction with herpes or EBV antibodies

B. Interference from medication

C. Cross-reaction with HLA antigens in the antigen preparation

D. Possible technical error

C Multiparous women often have HLA antibodies. The Western blot antigens are derived from HIV grown in human cell lines having HLA antigens. A cross reaction with HLA antigen(s) in the Western blot could have occurred.

Interpret the following results for HIV infection. ELISA: positive; repeat ELISA: negative; Western blot: no bands

A. Positive for HIV

B. Negative for HIV

C. Indeterminate

D. Further testing needed

B These results are not indicative of an HIV infection and may be due to a testing error in the first ELISA assay. Known false-positive ELISA reactions occur in autoimmune diseases, syphilis, alcoholism, and lymphoproliferative diseases. A sample is considered positive for HIV if it is repeatedly positive by ELISA or other screening method and positive by a confirmatory method.

Interpret the following results for HIV infection. HIV 1,2 ELISA: positive; HIV-1 Western blot: indeterminate; HIV-1 p24 antigen: negative

A. Positive for antibodies to human

immunodeficiency virus, HIV-1

B. Positive for antibodies to human

immunodeficiency virus, HIV-2

C. Cross reaction; biological false-positive result

D. Additional testing required

D The indeterminate Western blot and negative p24 antigen assay indicate that HIV-1 infection is

unlikely, However, additional testing is required to determine if the patient has antibodies to HIV-2 or if this could be a false-positive ELISA assay.

What is the most likely explanation when antibody tests for HIV are negative but a polymerase chain reaction test performed 1 week later is positive?

A. Probably not HIV infection

B. Patient is in the "window phase" before antibody production

C. Tests were performed incorrectly

D. Clinical signs may be misinterpreted

B In early seroconversion, patients may not be

making enough antibodies to be detected by

antibody tests. The period between infection with

HIV and the appearance of detectable antibodies is called the window phase. Although this period has been reduced to a few weeks by sensitive enzyme immunoassays, patients at high risk or displaying clinical conditions associated with HIV disease should be tested again after waiting several more weeks.

What criteria constitute the classification system for HIV infection?

A. CD4-positive T-cell count and clinical

symptoms

B. Clinical symptoms, condition, duration, and number of positive bands on Western blot

C. Presence or absence of lymphadenopathy

D. Positive bands on Western blot and

CD8-positive T-cell count

A The classification system for HIV infection is based upon a combination of CD4-positive T-cell count (helper T cells) and various categories of clinical symptoms. Classification is important in determining treatment options and the progression of the disease.

What is the main difficulty associated with the

development of an HIV vaccine?

A. The virus has been difficult to culture; antigen extraction and concentration are extremely laborious

B. Human trials cannot be performed

C. Different strains of the virus are genetically diverse

D. Anti-idiotype antibodies cannot be developed

C Vaccine development has been difficult primarily because of the genetic diversity among different strains of the virus, and new strains are constantly emerging. HIV-1 can be divided into two main subtypes designated M (for main) and O (for outlier). The M group is further divided into 9 subgroups, designated A-J (there is no E subgroup), based upon differences in the nucleotide sequence of the gag gene. Two remaining subtypes are designed N (non M and non O) and P (a subtype related to SIVgor). A vaccine has yet to be developed that is

effective for all of the subgroups of HIV-1.

Which CD4:CD8 ratio is most likely in a patient with acquired immunodeficiency syndrome (AIDS)?

A. 2:1

B. 3:1

C. 2:3

D. 1:2

D An inverted CD4:CD8 ratio (less than 1.0) is a common finding in an AIDS patient. The Centers for Disease Control and Prevention requires a CD4-positive (helper T) cell count of less than 200/μL or 14% in the absence of an AIDS-defining illness (e.g., Pneumocystis carinii pneumonia) in the case surveillance definition of AIDS.

What is the advantage of 4th-generation rapid HIV tests over earlier rapid HIV tests?

A. They use recombinant antigens

B. They detect multiple strains of HIV

C. They detect p24 antigen

D. They are quantitative

C Both 3rd-generation and 4th-generation rapid tests for HIV use recombinant and synthetic HIV antigens conjugated to a solid phase. The multivalent nature of these tests allows for detection of less common subgroups of HIV-1 and simultaneous detection of both HIV-1 and HIV-2. However, the 4th-generation assays also use solid-phase antibodies to p24 antigen to detect its presence. Because p24 antigen appears

before antibodies to HIV, 4th-generation tests can detect infection 4-7 days earlier than tests based on antibody detection alone.

Which method is used to test for HIV infection in infants who are born to HIV-positive mothers?

A. ELISA

B. Western blot test

C. Polymerase chain reaction

D. Viral culture

C ELISA and Western blot primarily reflect the presence of maternal antibody. The PCR uses small amounts of blood and does not rely on the antibody response. PCR amplifies small amounts of viral nucleic acid and can detect less than 200 copies of viral RNA per milliliter of plasma. These qualities make PCR ideal for the testing of infants. Nucleic acid methods for HIV RNA include the Roche Amplicor reverse- transcriptase assay, the branched DNA (bDNA) signal amplification method, and the nucleic acid sequence-based amplification (NASBA) method.

What is the most likely cause when a Western blot or ELISA is positive for all controls and samples?

A. Improper pipetting

B. Improper washing

C. Improper addition of sample

D. Improper reading

B Improper washing may not remove unbound enzyme conjugated anti-human globulin, and every sample may appear positive.

What constitutes a diagnosis of viral hepatitis?

A. Abnormal test results for liver enzymes

B. Clinical signs and symptoms

C. Positive results for hepatitis markers

D. All of these options

D To diagnose a case of hepatitis, the physician must consider clinical signs as well as laboratory tests that measure liver enzymes and hepatitis markers.

Which of the following statements regarding infection with hepatitis D virus is true?

A. Occurs in patients with HIV infection

B. Does not progress to chronic hepatitis

C. Occurs in patients with hepatitis B

D. Is not spread through blood or sexual contact

C Hepatitis D virus is an RNA virus that requires the surface antigen or envelope of the hepatitis B virus for entry into the hepatocyte. Consequently, hepatitis D virus can infect only patients who are coinfected with hepatitis B.

All of the following hepatitis viruses are spread through blood or blood products except:

A. Hepatitis A

B. Hepatitis B

C. Hepatitis C

D. Hepatitis D

A Hepatitis A is spread through the fecal-oral route and is the cause of infectious hepatitis. Hepatitis A virus has a shorter incubation period (2-7 weeks) than hepatitis B virus (1-6 months). Epidemics of hepatitis A virus can occur, especially when food and water become , contaminated with raw sewage. Hepatitis E virus is also spread via the oral-fecal route and, like hepatitis A virus, has a short incubation period.

Which hepatitis B marker is the best indicator of early acute infection?

A. HBsAg

B. HBeAg

C. Anti-HBc

D. Anti-HBs

A Hepatitis B surface antigen (HBsAg) is the first

marker to appear in hepatitis B virus infection. It is

usually detected within 4 weeks of exposure (prior

to the rise in transaminases) and persists for about

3 months after serum enzyme levels return to

normal.

Which is the first antibody detected in serum after infection with hepatitis B virus (HBV)?

A. Anti-HBs

B. Anti-HBc IgM

C. Anti-HBe

D. All are detectable at the same time

B Antibody to the hepatitis B core antigen (anti-HBc) is the first detectable hepatitis B antibody. It persists in the serum for 1-2 years postinfection and is found in the serum of asymptomatic carriers of HBV. Because levels of total anti-HBc are high after recovery, IgM anti-HBc is a more useful marker for acute infection. Both anti-HBc and anti-HBs can persist for life, but only anti-HBs is considered protective.

Which antibody persists in low-level carriers of

hepatitis B virus?

A. IgM anti-HBc

B. IgG anti-HBc

C. IgM anti-HBe

D. IgG anti-HBs

B IgG antibodies to the hepatitis B core antigen

(anti-HBc) can be detected in carriers who are

HBsAg and anti-HBs negative. These persons are

presumed infective even though the level of HBsAg is too low to detect. No specific B core IgG test is available, however. This patient would be positive in the anti-B core total antibody assay and negative in the anti-HB core IgM test.

What is the most likely explanation when a

patient has clinical signs of viral hepatitis but tests

negative for hepatitis A IgM, hepatitis B surface

antigen, and hepatitis C Ab?

A. Tests were performed improperly

B. The patient does not have hepatitis

C. The patient may be in the "core window"

D. Clinical evaluation was performed improperly

C The patient may be in the "core window," the period of hepatitis B infection when both the surface antigen and surface antibody are undetectable. The IgM anti-hepatitis B core and the anti-hepatitis B core total antibody assays would be the only detectable markers in the serum of a patient in the core window phase of hepatitis B infection.

Which hepatitis B markers should be performed

on blood products?

A. HBsAg and anti-HBc

B. Anti-HBs and anti-HBc

C. HBeAg and HBcAg

D. Anti-HBs and HBeAg

A Blood products are tested for HBsAg, an early

indicator of infection, and anti-HBc, a marker that may persist for life. Following recovery from HBV infection, some patients demonstrate negative serology for HBsAg and anti-HBs but are positive for anti-HBc. Such patients are considered infective.

Which hepatitis antibody confers immunity

against reinfection with hepatitis B virus?

A. Anti-HBc IgM

B. Anti-HBc IgG

C. Anti-HBe

D. Anti-HBs

D Anti-HBs appears later in infection than anti-HBc and is used as a marker for immunity following infection or vaccination rather than for diagnosis of current infection.

Which test, other than serological markers, is most

consistently elevated in viral hepatitis?

A. Antinuclear antibodies

B. Alanine aminotransferase (ALT)

C. Absolute lymphocyte count

D. Lactate dehydrogenase

B ALT is a liver enzyme and may be increased in hepatic disease. Highest levels occur in acute viral hepatitis, reaching 20-50 times the upper limit of normal.

If only anti-HBs is positive, which of the following

can be ruled out?

A. Hepatitis B virus vaccination

B. Distant past infection with hepatitis B virus

C. Hepatitis B immune globulin (HBIG) injection

D. Chronic hepatitis B virus infection

D Persons with chronic HBV infection show a positive test result for anti-HBc (IgG or total) and HBsAg but not anti-HBs. Patients with active chronic hepatitis have not become immune to the virus.

Interpret the following results for EBV infection:

IgG and IgM antibodies to viral capsid antigen

(VCA) are positive.

A. Infection in the past

B. Infection with a mutual enhancer virus such

as HIV

C. Current infection

D. Impossible to interpret; need more information

C Antibodies to both IgG and IgM VCA are found in a current infection with EBV. The IgG antibody may persist for life, but the IgM anti-VCA disappears within 4 months after the infection resolves.

Which statement concerning non-Forssman

heterophile antibody is true?

A. It is not absorbed by guinea pig antigen

B. It is absorbed by guinea pig antigen

C. It does not agglutinate horse RBCs

D. It does not agglutinate sheep RBCs

A Non-Forssman antibody is not absorbed by guinea pig antigen. This is one of the principles of the Davidsohn differential test for antibodies to IM. These antibodies are non-Forssman; they are absorbed by sheep, horse, or beef RBCs but not by guinea pig kidney. Therefore, a heterophile titer remaining higher after absorption with guinea pig kidney than with beef RBCs indicates IM.

Given a heterophile antibody titer of 224, which

of the following results indicate IM?

Absorption with Absorption with Beef

Guinea Pig Kidney Cells

A.Two-tube titer reduction Five-tube titer reduction

B.No titer reduction No titer reduction

C.Five-tube titer reduction Five-tube titer reduction

D.Five-tube titer reduction No titer reduction

A Antibodies to infectious mononucleosis (non-

Forssman antibodies) are not neutralized or absorbed by guinea pig antigen (but are absorbed by beef cell antigen). A positive test is indicated by at least a four-tube reduction in the heterophile titer after absorption with beef cells and no more than a three-tube reduction in titer after absorption with guinea pig kidney.

Given a heterophile antibody titer of 224, which

of the following results indicate serum sickness?

Absorption with Absorption with Beef

Guinea Pig Kidney Cells

A.Two-tube titer reduction Five-tube titer reduction

B.No titer reduction No titer reduction

C. Five-tube titer reduction Five-tube titer reduction

D.Five-tube titer reduction No titer reduction

C In serum sickness, antibodies are neutralized by both guinea pig kidney and beef cell antigens, and at least a three-tube (eightfold) reduction in titer should occur after absorption with both.

Given a heterophile antibody titer of 224, which

of the following results indicate an error in testing?

Absorption with Absorption with Beef

Guinea Pig Kidney Cells

A.Two-tube titer reduction Five-tube titer reduction

B.No titer reduction No titer reduction

C.Five-tube titer reduction Five-tube titer reduction

D.Five-tube titer reduction No titer reduction

B An individual with a 56 or higher titer in the

presumptive test (significant heterophile antibodies) has either Forssman antibodies, non-Forssman antibodies, or both. A testing error has occurred if no reduction in the titer of antibody against sheep RBCs is observed after absorption because absorption should remove one or both types of sheep RBC agglutinins.

Blood products are tested for which virus before

being transfused to newborns?

A. EBV

B. Human T-lymphotropic virus II (HTLV-II)

C. Cytomegalovirus (CMV)

D. Hepatitis D virus

C CMV can be life threatening if transmitted to a

newborn through a blood product. HTLV-II is a rare virus, which like HIV, is a T-cell tropic RNA retrovirus. The virus has been associated with hairy cell leukemia, but this is not a consistent finding.

What is the endpoint for the antistreptolysin O

(ASO) latex agglutination assay?

A. Highest serum dilution that shows no

agglutination

B. Highest serum dilution that shows agglutination

C. Lowest serum dilution that shows agglutination

D. Lowest serum dilution that shows no

agglutination

B The latex test for ASO includes latex particles coated with streptolysin O. Serial dilutions are prepared and the highest dilution showing agglutination is the endpoint.

Interpret the following ASO results:

Tube Nos. 1-4 (Todd unit 125): no hemolysis; Tube No. 5

(Todd unit 166): hemolysis

A. Positive Todd unit 125

B. Positive Todd unit 166

C. No antistreptolysin O present

D. Impossible to interpret

A An ASO titer is expressed in Todd units as the last tube that neutralizes (no visible hemolysis) the streptolysin O (SLO). Most laboratories consider an ASO titer significant if it is 166 Todd units or higher. However, people with a recent history of streptococcal infection may demonstrate an ASO titer of 166 or higher; demonstration of a rise in titer from acute to convalescent serum is required to confirm a current streptococcal infection. ASO is commonly measured using a rapid latex agglutination assay. These tests show agglutination when the ASO concentration is

200 IU/mL or higher.

Which control shows the correct result for a valid

ASO test?

A. SLO control, no hemolysis

B. Red cell control, no hemolysis

C. Positive control, hemolysis in all tubes

D. Hemolysis in both SLO and red cell control

B The red cell control contains no SLO and should

show no hemolysis. The SLO control contains no

serum and should show complete hemolysis. An

ASO titer cannot be determined unless both the

RBC and SLO controls demonstrate the expected

results.

A streptozyme test was performed, but the result

was negative, even though the patient showed

clinical signs of a streptococcal throat infection.

What should be done next?

A. Either ASO or anti-deoxyribonuclease B

(anti-DNase B) testing

B. Another streptozyme test using diluted serum

C. Antihyaluronidase testing

D. Wait for 3-5 days and repeat the streptozyme

test

A A streptozyme test is used for screening and

contains several of the antigens associated with

streptococcal products. Because some patients

produce an antibody response to a limited number of streptococcal products, no single test is sufficiently sensitive to rule out infection. Clinical

sensitivity is increased by performing additional tests when initial results are negative. The streptozyme test generally shows more false positives and false negatives than ASO and anti-DNase. A positive test for antihyaluronidase occurs in a smaller number of patients with recent streptococcal infections than ASO and anti-DNase.

Rapid assays for influenza that utilize specimens

obtained from nasopharyngeal swabs detect:

A. IgM anti-influenza

B. IgA anti-influenza

C. IgA-influenza Ag immune complexes

D. Influenza antigen

D The rapid influenza assays are antigen detection

methods. They are designed to detect early infection, before antibody is produced.