The values of synthetic substrates in the improvement of diagnostic tests for haemostatic function

The accumulated evidence suggests that synthetic substrates measure a similar biological expression as their natural counterpart with, in some cases, a better precision and simplicity of operation. Proteolytic enzymes are involved in a variety of physiological and pathological processes extending from blood coagulation to the release of specific enzymes from certain cells and bacteria. The variation in the level of these proteases, and their inhibitors in plasma or in cells, will be an excellent indicator of any malfunction in the particular system. Excellent agreement between these new generation tests and other conventional methods particularly in measuring fibrinolytic components is seen, and the assay time is cut from hours to a matter of minutes using a reaction rate analyser. Some discrepancy in the estimated potency was observed between methods used for the assay of thrombin, FVIII and several other clotting factors and their inhibitors. There has been methodological improvement and, in some cases, the cause of discrepancy has been revealed. Nevertheless, greater emphasis should still be given to standardization problems. It is, therefore, suggested that until the problems of standardization of various assay methods are resolved and the complications due to non-specificity in chromogenic methods and non-selectivity in clotting tests are overcome, the ratio of amidolytic to clotting activities should be included in the request for potency estimations and in the diagnostic assessment. Whether or not the use of substrates should be complementary or supplementary is left to individual centres according to their particular circumstances.