Prolonged Prothrombin Time After Discontinuing Vitamin K Antagonist/Commentary

Both laboratories found a strong presence of LA. Because our patient was using vitamin K antagonists, the patient's plasma was diluted with normal plasma to reduce the effect of medication before performing LA coagulation assays. The influence of antiphospholipid antibodies on INR values is dependent on the reagent used by the clinical laboratory. [...]doubtful results in coagulation testing should always be discussed with a laboratory professional, as was done in this case by the patient himself. [...]they should work to establish an institutional requirement for baseline PT/INR testing before initiating VKA therapy and monitor compliance as a patient safety quality indicator. [...]they should provide a PT mixing study test (1:1 patient plasma and pooled normal plasma) to investigate unexplained prolonged PT results.