Page 9 - Clinical Biochemistry 08PB804

(inhibiting thrombin activity), Citrate or ethylenediaminetetraacetic acid (EDTA) (bind
calcium). This preparation should be mixed immediately and thoroughly to avoid clotting.

• Serum is still the most preferred specimen in clinical chemistry as the anticoagulant
interference is eliminated.

• Serum is clearer than plasma because of fewer proteins. Proteins are sometimes considered
as interfering substances in some tests as they react with the reagent and thereby yield
inaccurate results.

Haemolysis can interfere with lab results due to several processes:

• Leakage of analytes from lysed erythrocytes may cause a false increase in the amount of
analyte measured in serum if the analyte is normally present in a greater amount inside the
RBC than in plasma.

• Color interference (tinting the serum pink or red) can cause false increases when using a
spectrophotometer. Hemoglobin, bilirubin and protein are a few of the analytes affected by
hemolysis. Equipment not been calibrated to standard form, therefore giving wrong
measurements.

• Sometimes erythrocyte constituents can react with analytes, causing a false decrease. This
can occur when testing for carbon dioxide, thyroxin and insulin.

Other types of blood samples:

• Blood: The fluid that circulates through the heart, arteries, capillaries, and veins.

• Blood cell: Any cellular element of the blood including erythrocytes, leucocytes, and
platelets.

• Blood group: The cell membrane properties that provide the specific antigenicity of blood
groups are called agglutinogens as they agglutinate or clump in the presence of their specific
antibody.

• Cord blood: The blood contained in the vessels of the umbilical cord at the time of birth.

• Occult blood: Blood present in such small amounts that its presence can be ascertained
only by chemical analysis or by spectroscopic or microscopic examination; particularly the
blood found in stools.