Step One
The first step in a mixing study is creating a 1:1 mix of patient and pooled normal plasma.
Before beginning the mixing study, it is essential to ensure that the pooled normal plasma the laboratory uses has normal coagulation factor levels; manufacturers will often supply this information.
The mix can be created by aliquoting equal parts of patient plasma to pooled normal plasma. The sample must be mixed by gentle inversion or by slowly pipetting the mixture up and down. This ensures the proper incorporation of the factors in the sample.
Note: It is not appropriate to use PT/aPTT control material or a single patient plasma sample with normal PT and aPTT test values to replace pooled normal plasma. If pooled plasma is prepared in the laboratory, a minimum of 20 plasma samples from healthy donors should be used. Commercial products are also acceptable.
