should be free from detergents, acids and alkalies.

These chemicals have a varying effect on pH. Change

in pH effects factor stability. Detergents inhibit reactive

characteristics of the sample/reagent mixture.

• Ideally the cleaning of glassware used in coagulation

tests should be the responsibility of one individual

and should be handled separately from routine

laboratory glassware. Alternatively, disposable

labware should be used.

¾ The specimen to be tested for coagulation studies must

be used preferably immediately.

• As most of coagulation factors are time as well as

temperature labile it is of utmost importance that

they should not be subjected to high temperatures

and tests be performed as early as possible, preferably

immediately.

• If specimens are held at 22 to 24oC then they must be

tested within 2 hours and if the specimens are held

at 2 to 4oC then they must be tested within 3 hours.

• Plasma samples held at 4 to 8oC for prolonged

periods may undergo cold activation leading to

erroneous results.

• Samples obtained for factor assays and tests for

fibrinolysis should be stored in crushed ice if a delay

in testing is anticipated.

• Citrated blood for platelet aggregation studies should

remain in capped tubes at room temprature (20 to

25o C) before testing.

¾ The sample collected must be stored tightly capped.

• If the tubes are not capped the samples will absorb

atmospheric CO2 leading to shift in pH to an

unacceptable range. This hampers factor stability

and accuracy of results.

• Centrifugation speed and time are of absolute

importance in coagulation studies. The PT test uses

PPP while the APTT test uses PFP.

• Excessive centrifugation may destroy clotting factors

due to the heat generated during centrifugation.

• Under centrifugation would lead to the presence

of platelets in plasma sample, which could lead to

activation of clotting mechanism in vitro which leads

to erroneous results.