hematology

Hematology

the study of blood

bone marrow

red blood cells

white blood cells

platelets

identification of cells

correlation abnormalities with disease

study of coagulation and hemostasis

intro to hematology

average person has 5 L of blood (5-6 qt)

separated into 3 L of plasma and 2 L of cells

plasma is liquid derived from the intestines and organs

the cells are formed mainly by the bone marrow

the blood can be thought of as a tissue

without plasma, cells cannot circulate

without cells, vascular fluid alone cannot maintain life

cells found in the blood

erythrocytes (red blood cells)

leukocytes (white blood cells)

granulocytes (polymorphonuclear leukocytes)

• neutrophils

• eosinophils

• basophils

no granulocytes 9agranulocytes)

• lymphocytes

• monocytes

platelets or thrombocytes

why do we study blood?

red blood cell disorders

disorders of RBCs are grouped into

anemias - reduction in circulating red blood cells or decreased hemoglobin concentration

may be due to

• blood loss

• impaired heme production

• impaired DNA synthesis

• increased destruction (hemolytic disorders)

polycythemias

• abnormal increases in circulating red cells

• leading to hyper viscosity

leukocyte disorders

disorders of the leukocytes are termed either

• leukocytosis (an increased number of cells)

  • infections - viral, bacterial, fungal, tubercular

  • leukemia

• leukopenia (a decreased number of cells)

  • agranulocytosis

  • granulocytopenia

  • ionizing radiation

  • chemotherapy

platelet disorders

thrombocytopenia

• a decreased number of platelets

• manifests itself in hemorrhage

thrombocytosis

• an increased number of platelets

platelet dysfunction

• disorders of platelet aggregation

• disorders of platelet adhesion

• disorders of platelet secretion

collection procedures - skin puncture

capillary blood obtained from:

• the tip of a finger or earlobe in adults

• lateral heel in infants

• tip of the finger in infants over 1 year

properly identify the patient using 3 forms of ID

• name, DOB, medical record number, ask them to identify themselves

puncture site is wash with disinfectant (70% isopropyl alcohol)

allowed to air dry

punctured no deeper than 2 mm

using a sterile disposable lancet

dispose in sharps container

skin puncture continued

if povidone-iodine (betadine) is used

must be allowed to dry thoroughly to be effective

first drop of blood is wiped away with sterile gauze

subsequent drops are collected

clinical alert:

avoid squeezing the extremity to obtain blood

doing this will alter composition of blood

hemodilution

venipuncture

venipuncture

• necessary for most tests

• anti-coagulation

• larger quantities of blood

site

• median cubital vein

• median antebrachial

• cephalic

no variation in blood values if specimens are obtained from different veins

procedure for venipuncture

• properly identify the patient suing 3 forms of ID

  • name, DOB, medical record number, ask them to identify themselves

• a tourniquet is placed to cause venous congestion

• puncture site is cleansed with 70% iso-propyl alcohol and allowed to air dry

• the vein is cleanly punctured with a sterile needle

  • syringe or a vacutainer system

• release the tourniquet pressure

• remove needle and apply sterile gauze with pressure

• make sure patient stops bleeding

• cover puncture site with an adhesive bandage

clinical alert

do not allow the tourniquet to remain in place for prolonged periods of time >1 minute

causes hemoconcentration of bloof cells

• falsely elevates cell counts

do not collect blood from arm with IV fluids

• causes hemodilution

• may collect blood from below the IV site or use other arm

blood for legal alcohol testing

• do not use alcohol disinfectant

• falsely elevates test results

specimens

whole blood

• anti-coagulant

plasma

• fluid fraction

• separated from anti-coagulated blood

serum

• fluid fraction

• separated from clotted blood

basic blood tests

complete blood count (CBC)

basic screening test in all patients

one of the most frequently ordered lab procedures

CBC consists of

White blood count (WBC)
 Red blood count (RBC)
 Hematocrit (HCT)
 Hemoglobin (Hgb)
 Red blood cell indices
 Mean corpuscular volume (MCV)
 Mean corpuscular hemoglobin (MCH)
 Mean corpuscular hemoglobin concentration (MCHC)
 Red cell distribution width, (RDW)
 Platelet count (often included in CBC)
 White cell Differential count (Diff)
 White cell Differential count (Diff)

Ethylene-diamine tetra acetic acid (K2EDTA)

Purple top tube
 Calcium chelator
 preventing coagulation to occur.
 Used in cell counts and morphologic examination
 Blood smears should be made & examined within 2
hours of collection.

 Alert:
 EDTA-induced pseudothrombocytopenia
 Platelet clumping may occur
 “EDTA phenomenon”
 Platelet Satelitism
 Collect blood in Citrate tube, repeat PLT count

sodium citrate

Blue top tube
 Calcium chelator
 Used in coagulation studies
 Blood to anticoagulant ration must be 9:1
 Low specimen ratio, elevates coag results

Used in Platelet Satellitism
 Platelet count has to be multipled by 1.1 in order to correct for
anticoagulant volume

heparin

Green top tube

 Lithium Heparin

 Mechanism of action:
 inhibits the action of thrombin.
 Anti-thrombin activity

 Used for most chemical testing and

 Not recommended for hematology testing
 Heparin distorts cellular morphology
 Interferes with coagulation studies.

 Not recommended for Lithium assays.
 Falsely elevates Li values
 Used in treatment of Bi-polar disorders

quality management system

QMS in the laboratory includes all processes,
procedures and resources to ensure quality
results
 Quality Assurance focuses on the processes
 Provide the best services to maintaining
excellence in patient care
 It is the sum of three components:
 Pre-analytical
 Analytical
 Post analytical

Pre-analytical

Test Utilization
 Correct ordering of tests
 Patient Preparation
 Patient Identification
 Proper Collection of Specimen
 Timely Specimen Transport
 Proper Specimen Handling
 Specimen Separation
 Proper Personnel Education & training

Analytical

Proper storage, labeling and use of reagents
 Calibration of pipetting devices
 Preventative maintenance of instruments
 Checking temperatures of refrigerators/incubators
 Periodic checking of centrifuge speeds
 Analytical Methodology verification
 Use of Standards and Calibration
 Procedures Manuals are up to date
 Verification of Reference intervals
 Technical Staff Competencies
 Inventory Control of Materials
 Monitoring Method Problems and Remedies

post analytical

Verification of Final Reports
 Review of test results for possible errors
 Reports that are easy to read and interpret
 Procedures for informing the physician of results
that require immediate attention (critical values)
 Timeliness of reporting values to patient charts
 Constant interaction with the institution to ensure
quality in direct patient care as a result of lab
testing

types of quality control

internal

• continuous evaluation of reliability of the daily works of the lab with validation of tests

• primary tool required is called a control - a specimen with a predetermined range of result values, processed in the same manner as patient sample

• if the result of a test on a control sample is different from its known value, this indicates a problem in the equipment or the methods being used

external

• evaluation by an outside agency of the comparability a laboratory’s testing to a source outside the laboratory

• this comparison can be made to the performance of a peer group of laboratories or to the performance of a reference laboratory

• the analysis of performance is retrospective

internal quality control

physical measurement of assayed controls

• every 8 hours, run 2 levels of controls

• one level within the normal range, one level outside the normal range

application of statistical analysis of quality assurance

• moving average of RBC indices

• delta check

control material

needs to have same matrix as patient specimen

acceptable limits predetermined by manufacturer

• within 2 SD or two standard deviations of given mean

• plotted on LEvy-Jenning’s Chart

• westgard rules

accuracy

describes how close a test result is to the true value

implies freedom of error

precision

describes how close the test results are to one another when repeat analysis of specimens is performed

precision refers to the reproducibility of test methods and results

precision is freedom from variation

accuracy and precision

accuracy is a measure of rightness

refers to closeness to the true value

precision is measure of exactness

refers to reproducibility of the test

basic statistical concepts

mean - arithmetic average value of a group of data

mean = Ex/n

standard deviation

expression of variation of data around the mean

measure of variability or precision of a test method

SD = √variance

coefficient of variation

Expression of the standard deviation
as a percentage of the mean
 Useful for comparison of data sets
with different units

Levy Jennings Control Charts

QC charts graphically display data values versus time.
 Confidence limits or control limits are calculated from the
mean and SD:
 Mean ± 2 SD = 95% confidence limits
 Control values are plotted on the y axis; time is plotted on
the x axis.
 The mean is plotted as a center line with the + 2SD above
and the - 2SD below the mean.
 Within the confidence limits, control results are assumed to
be accurate.
 If control results are outside the Confidence limits, it said
to be “out of control”
- Patient results cannot be reported

Errors