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.
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
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).
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.
All hematological testing utilizes anticoagulated blood.
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.
If the specimen is deeply icteric, falsely elevated cholesterol
results may be obtained.
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.
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
Blood specimens older than 24 hours cannot be adequately tested
for some analytes. Particularly sensitive are most Hematology
tests including Blood Coagulation procedures.
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