Basic Laboratory Tests of Hemostatic Function - Mixing Studies

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Basic Laboratory Tests of Hemostatic Function - Mixing Studies

  • Performed after an unexpected, prolonged PT or APTT is encountered to determine if the problem stems from a factor deficiency or the presence of an inhibitor.
  • To perform the test, the patients’ plasma is mixed with an equal volume of pooled normal plasma, and then a PT and APTT are performed off the mixture. Testing is performed on the "mix" with and without an incubation period. The incubated sample is important to detect the presence of time/temperature dependent inhibitors.
  • If the addition of the pooled plasma brings the resultant values into normal range, then the pooled plasma contained factors the patient's sample was deficient in, and the patient has a factor deficiency.
  • If the results are not “corrected” or brought back into normal range after the addition of pooled normal plasma, then an inhibitor may be present.
  • The next step in the diagnostic sequence of events, if correction has occurred, is to perform a factor assay, to determine which specific factor is lacking.