From Sylvia Bunting, Children’s Healthcare of Atlanta: We do an immediate and incubated mixing study. For deciding on whether there is a time-dependent inhibitor, what criteria do you use to decide that the PTT was prolonged after incubation? Any prolongation beyond the immediate mix PTT? Thanks.
Hi, Sylvia, and thank you for your question. If the PTT immediate mix corrects, prepare a new patient plasma-normal control plasma mix and incubate. Simultaneously incubate an aliquot of the normal control plasma. Perform a PTT on the incubated mix and the incubated control plasma. If the mix result is prolonged by more than 13% beyond the incubated control plasma, the result is uncorrected, indicating a time-dependent inhibitor. Less than 10% difference indicates correction and no inhibitor. Repeat, ensuring the patient plasma was platelet poor, if the ratio is between 10 and 13% longer than the control.
Also, please check out audio module 25 for more details on mixing studies. Geo.