From “Balasubm” at Einstein Healthcare in Philadelphia: Hi George, I have a 74 year old female renal dialysis patient who is asymptomatic with prolonged prothrombin time (PT) of 38 seconds and activated partial thromboplastin time (APTT, PTT) of 116 seconds, with a normal thrombin time. Mixing performed immediately reveals PT of 30.3 seconds (N 9.5-13.5) and APTT of 84.3 seconds (N 22-38). After incubation the PT went to 31.6 seconds and APTT to 86.6 seconds. The specimen was drawn from the dialysis catheter, however, these lines do not use heparin. Could you please tell us what you think these results mean?
Hello, and thank you for your question. Yes, given that there was no correction upon immediate mixing, you have presumptive lab evidence for a lupus anticoagulant (LA). The normal thrombin time supports the absence of heparin, and additionally, the absence of either of the new oral anticoagulants, dabigatran or rivaroxaban. I recommend you perform an LA profile on the specimen, typically one that uses a dilute Russell viper venom time kit and Sta-Clot LA kit for confirmation.
I know of no other therapeutic used in renal dialysis that could account for the prolonged PT and PTT and the lack of correction, however the patient’s physician will want to order a confirmatory LA profile 12 weeks or more from this positive sample, and it may be possible to collect the new specimen at a time between dialysis treatments to eliminate the possibility of interference.