Abnormal Coagulation Test Results
A common problem is an unexplained increase in the PT and/or PTT. The first thing to do is get a fresh sample and repeat the test. Another consideration is heparin. It is possible that the blood sample was mistakenly drawn though a running line. Interference by heparin can be detected by absorbing the heparin with a resin (“Heparsorb”) or by using an enzyme to digest the heparin (“Hepzyme”). Also, the patient's history should be checked: Is the patient on any anticoagulants? Does the patient have liver disease? Provided that the abnormal result is reproduced on a good specimen and there is no obvious explanation from the history, the next thing to do is a mixing study. If the mixing study shows correction and no prolongation with incubation, factor assays will need to be done to look for factor deficiency, starting with VIII and IX since they are the most common deficiencies. It is useful to do a few vitamin K–dependent and a few nonvitamin K–dependent factors to be sure that the problem is not accidental or surreptitious warfarin ingestion.
Read more about this topic: Mixing Study
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