ARTIFACTUAL PROLONGATION OF THE ACTIVATED PARTIAL THROMBOPLASTIN TIMEMIMICKING A COAGULOPATHY - A LESSON RELEARNED

A markedly prolonged activated partial thromboplastin time (APTT) was observed in a 61-year-old woman with bruising and a decreasing hematoc rit. Coagulation laboratory evaluation was sought to determine the cau se of the prolonged APTT and bleeding. Evaluation demonstrated that, r ather than identifying a coagulopathy, the APTT prolongation was most likely artifactual. The APTT was actually very short. With a combinati on of a relatively strong activating APTT reagent (Dade Actin; Dade, M iami, FL) and a fixed lag phase in the automated coagulation instrumen t (16 seconds), the clot formed before the instrument began to read. T hus, during the period of observation (120 seconds), no change in opti cal density was observed. This was interpreted by the laboratory as '' > 120 seconds.'' This case reminds those involved in the performance a nd interpretation of APTTs of the importance of a manual or visual met hod of verifying markedly prolonged APTTs.