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Some analytes may be reported erroneously if the serum is not promptly removed from the clot, or if the barrier tube is not centrifuged after the clot has formed.

Major discrepancies are low glucose, high potassium and LD. Additionally, if hemolysis takes place during initial processing and venipuncture, or if prolonged contact with the clot takes place, elevation in cholesterol, creatinine, iron, phosphorus, calcium and most enzymes will be found. Hemolyzed hematological specimens are unsuitable for testing.

Quantity Not Sufficient (QNS):
Most hematology tests require that a full tube of blood be obtained. This is because there is a defined quantity of anticoagulant in each tube and the ratio of this to the blood volume has to be exact to ensure quality results. Particularly important are blue-top tubes used for Blood Coagulation tests. For prothrombin time, activated partial thromboplastin time and fibrinogen determinations exactly 4.5 mL of blood must be obtained (a full tube).

For CBCs a "short draw" lavender tube will result in red cell crenation, reduced MCV and hematocrit, and possible changes in leukocyte morphology, platelets and total leukocyte counts.

Clotted Specimens:
All hematological testing utilizes anticoagulated blood.

For blood counts, a lavender top tube containing the anticoagulant EDTA is required. All specimens should be collected and the tube filled to the limit of the vacuum. Clotted samples, either macroscopic or microscopic in nature, cannot be processed for CBC testing, as such results will produce false leukopenia, low red cell counts, and aberrant red cell indices. As the equipment used to test blood counts incorporates a clot detector, it is occasionally possible that specimens that appear macroscopically normal will have small microscopic clots that are detected which will produce incorrect results. Similarly, small clots found in blue top tubes (for coagulation tests) will result in falsely prolonged test results.

Icteric Specimens:
If the specimen is deeply icteric, falsely elevated cholesterol results may be obtained.

Lipemic Specimens:
Lipemia can falsely elevate ALT and AST. Additionally, it can indicate that the patient did not adequately fast for 12-18 hours before having the specimen collected. In this situation, glucose and triglycerides will be elevated.

Decreased Bilirubin:
Bilirubin is photodegradable. Prolonged exposure of the specimen to bright light will produce depressed results.

Decreased CO2 Levels:
Carbon dioxide levels are decreased if the specimen is not tested promptly. CO2 escapes from red cells in vitro, at a rate proportional to time. This can be minimized by keeping the stopper on the tube and by refrigeration.

Poor Cell Preservation:
Blood cells, particularly leukocytes become fragile and can be distorted morphologically if the specimen is older than 24 hours. In such situations, a reliable differential white cell count cannot be performed.

Old Specimens:
Blood specimens older than 24 hours cannot be adequately tested for some analytes. Particularly sensitive are most Hematology tests including Blood Coagulation procedures.

Alkaline Phosphatase:
The reference range for this analyte is that used for Adults. As the enzyme is increased in periods of bone growth, as well as in pathological bone disorders, the reference range for adolescents tends to be much higher than in adults. We will automatically provide adolescent reference ranges for all patients under 19 years of age if the age is clearly included on our test request form.

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