Her Coombs test was negative and her coagulation profile was within normal limits, with an international normalized ratio (INR) of 1.12 and activated partial thromboplastin time (APTT) of 27.2 seconds. A blood test to evaluate for ADAMTS13 activity was sent urgently to exclude thrombotic thrombocytopenic purpura (TTP) but results were not immediately available. This evidence concerns the gene ADAMTS13 and thrombotic thrombocytopenic purpura.