Coagulation Factor Assays |
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Coagulation factors may be deficient on a congenital or acquired basis. The APTT is used as the basis of the test when testing for Factors VIII, IX, XI, and XII; the prothrombin time (PT) is used for Factors II, V, VII, and X. The level of each coagulation factor is expressed as a percentage of its level in normal pooled or standardized reference plasma. The level of each coagulation factor required for normal hemostasis is as follows: 20% for Factor XI, 30-40% for Factors II, V, VII, VIII, IX, and X.
Specimen requirement is 4.5 mL of blood collected in a light blue top (citrate) tube. To avoid tissue fluid contamination, the tube should be drawn after collecting 5.0 mL of blood in a red top discard tube. Specimens should be delivered to the laboratory within 2 hours. If the transport time will be longer, the specimen should be centrifuged, the plasma separated into a plastic vial, and frozen.
The reference range for Factors II, V, VII, VIII, IX, X, and XII is 50 - 100%.
The reference range for Factor XI is 70 - 130%.
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