If the mixing study results suggest a factor deficiency, further testing will be required in order to discover which factor is deficient. In order to do this, you must first identify which factors are possibly involved. This can be done by referring back to the principles of the PT and aPTT test and their respective factor involvements.
When you have narrowed down the possible factors involved in the prolongation, the next step should be individual factor assays. These assays use a similar protocol to the original mixing study; however, pooled normal plasma is substituted with an individual factor-deficient plasma.