Serology Review, Dilutions, Titers - Lab 1

Serology

the scientific study of serum, plasma, and other body fluids

-these samples are used for diagnostic identification of antibodies or antigens (Ag-Ab rxns)

serum

liquid portion of the blood without clotting factors

-forms a clotted product

plasma

liquid portion of the blood containing clotting factors

Antigen (Ag)

a foreign substance from the environment (bacteria, virus, pollen, chemical, etc.) that when introduced to the body, may stimulate production of antibody (Ab)

• also called an immunogen when initiating an immune response

Antibody (Ab)

a large Y-shaped protein produced by B-cells (humoral immune response) used to identify and neutralize foreign objects (bacteria, viruses, pollen, and chemicals)

• also called immunoglobulin (Ig)

What are some types of serologic methods?

Agglutination, precipitation, flocculation, ELISA/ EIA, neutralization, hemagglutination inhibition

Precipitation

serologic method for when both Ag and Ab are soluble

• bind and form a precipitate of the Ag-Ab complex (immune complex) when Ag and Ab are in the Zone of Equivalence

• Can be performed in liquid or solid matrix—> turbidity/cloudiness, immunodiffusion-precipitin lines/rings

Flocculation

serologic method with a precipitation reaction

• soluble Ag-Ab complex adheres to carrier particles

  • RPR & VDRL - Syphilis

ELISA/ EIA

serologic method that uses enzyme labeling

• The Ab is labeled w/ an enzyme, Ag and Ab bind, substrate specific to enzyme is added, color is produced

  • ANA & Rapid strep

Neutralization

serologic method that involves neutralizing and Ag or Ab

• ASO: anti-streptolysin O neutralizes Streptolysin O from lysing RBCs

Hemagglutination inhibition

serologic method where agglutination of RBCs is inhibited

Serum Ab neutralizes virus

Immunofluorescence

a form of luminescence using fluorophores that absorb light at one wavelength and emit light at another wavelength

Usually the emitted light has a longer wavelength and lower energy than the absorbed light

• DFA and IFA

accuracy

ability of a test to match the results of an established test known as the reference method

highly accurate tests can obtain the same result when testing samples of known value

precision

reproducibility of a test when repeated in your own lab or in another lab

same result will occur with each repetition of the particular test

sensitivity

the probability (%) that a person w/ a disease or condition will test positive for that condition

• Having a value of 95% of this measure means that 95/100 people that have the disease will test positive; 5/100 will falsely test negative

• High ____ tests are excellent for screening purposes

specificity

the probability (%) that a person without a disease or condition will test negative

• Having a value of 95% of this measure means that 95/100 people that don’t have the disease will test negative; 5/100 will falsely test positive

• high ____ tests are excellent for confirmatory testing

Measures of quality control

external controls, internal controls, specimen collection and storage, reagent storage and expiration dates

external controls

positive control (high, low) and negative controls

internal controls

Built in, procedural, electronic

Titers

in immunology, performed to determine the concentration of an antibody present in a patient sample —> serial dilution of patient serum

expressed as the reciprocal of the highest dilution of patient serum in which antibody is detectable —> dilution in which the last measurable rxn occurred