Performing a mixing study will help to differentiate between a factor deficiency and a coagulation inhibitor as the cause of a prolonged PT or aPTT test result.
A mixing study is performed by mixing the patient plasma that has a prolonged PT or aPTT with normal pooled plasma. A PT and/or aPTT is then retested on the mixed sample.
If the cause of the prolonged PT and/or aPTT is a factor deficiency, or multiple factor deficiencies, the normal pooled plasma will increase the factor levels to the point of correcting the prolonged test result. However, the addition of normal pooled plasma will not correct the prolonged test result if the cause is a coagulation inhibitor.