Most clinical laboratories will use a 1:1 mix when performing mixing studies; however, some will use various dilutions of patient plasma and pooled normal plasma for their protocols.
In addition, the analysis of the mixing study involves interpreting the pre- and post-mix results. This can be performed using various methods including: the Rosner Index, the <70% correction formula, or a laboratories own calculation and cut-off value.
Finally, it is suggested that each laboratory test the sensitivity of their PT and aPTT reagents before running mixing studies. The sensitivity of the reagent system can be tested by running dilutions of the pooled normal plasma controls with specific factor deficient plasma. This ensures that the system will detect a normal result, even if the factor level is as low as 40%.
