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When coagulation screening tests are performed to verify normal function of the coagulation system (eg, preoperative, routine examination), they sometimes indicate an abnormality that may be unexplained (ie, prolonged clotting times). This consultation provides validation of the prolongation and as comprehensive a work-up as needed to define the abnormality.
Possibilities for a cause of prolongation include:
-Factor deficiency(ies), congenital or acquired
-Factor inhibitors (including Coumadin therapy)
-Dilution of specimen by anticoagulant if patient hematocrit is > or =55%
Determining cause of prolongation of prothrombin time or activated partial thromboplastin time
Screening for prolonged clotting times and determining the presence of factor deficiency(ies) or inhibitor (factor-specific, lupus-like, or the presence of heparin)
A interpretive report will be provided.
If patient hematocrit is > or =55%, the volume of citrate anticoagulant should be adjusted prior to submitting the specimen for analysis to avoid dilution of plasma by anticoagulant (see Clinical Reference-NCCLS Document H21-1).
Patient should not be receiving oral vitamin K inhibitor (eg, warfarin, Coumadin), heparin, low molecular weight heparin, hirudin (Refludan), argatroban, fibrinolytic agents (eg, streptokinase, tissue plasminogen activator) for optimal results. If necessary, testing may be performed on patients receiving these treatments. Medications affecting coagulation parameters must be noted on requisition for accurate interpretation of results.
If patient has been recently transfused or will be, it is best to perform this study pretransfusion, if possible.
An interpretive report will be provided.
Kamal AH, Tefferi A, Pruthi RK: MBBS. How to interpret and pursue an abnormal prothrombin time, activated partial thromboplastin time, and bleeding time in adults. Mayo Clin Proc 2007 Jul;82:864-873