DOI: 10.1373/Clinchem.2007.100818


A 47-year-old African American woman was evaluated for a prolonged prothrombin time (PT) result obtained before she underwent right total hip arthroplasty. The patient had no history of gastrointestinal or intracranial bleeding, epistaxis, or hemarthrosis. However, she reported a tendency toward easy limb bruising and menorrhagia, which required iron supplementation. She had a negative family history of abnormal bleeding. Initial laboratory studies included findings within reference intervals for complete blood cell count and activated partial thromboplastin time (aPTT) (30.8 s, reference interval 23–36 s), prolonged PT (20.3 s, reference interval 11.0–15.0 s), and International Normalized Ratio (INR) (1.78, reference interval 0.9–1.2). No preanalytical artifacts were identified, and the result of a repeat PT was also prolonged.