An Introduction to the Fundamentals of Coagulation: Laboratory Tests of Hemostatic Function

Tests of Hemostatic Function - Factor Assays

  • Used to determine the cause of an unexpected, prolonged PT or APTT.

  • This test is performed after mixing studies have been run, because factor assays are able to identify specific factor deficiencies or inhibitors.

  • Think of mixing studies as being the screening test, while factor assays are confirmatory tests for specific factor deficiencies.

  • The test itself is involves performing a PT and APTT, except that plasma known to be deficient in a specific factor type is combined with the patients plasma, comparing the resultant time to a standard curve.

  • The percent of activity, and amount of correction with normal plasma determines the specific factor deficiencies.


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