Quantification of coagulation factors and inhibitors. Still a special task

This is a very short review on quantitative coagulation factor assays for the beginner. For systematic training several excellent textbooks in German language are available. Quantitative functional assays of coagulation factors and of physiological inhibitor proteins are based on the principle of parallel-line or slope ratio bioassays. With the modern analyzers the test procedure follows the example of clinical chemistry: a single test plasma dilution read from an actual calibration curve, regular internal and external quality control. If there are unexpected results or a suspicion of haemophilia we recommend to repeat the assay with three different pre-dilutions of the test plasma. The resulting potency estimates should not deviate by more than 10-15% from their average. Otherwise the assay is invalid and requires further investigation (e.g. search for inhibitors). Special problems may complicate diagnostic activities. As an example discrepancies between factor VIII one-stage clotting and chromogenic assays are discussed.