Assay of heparin in plasma using a chromogenic substrate and its clinical applications.

The concentration of heparin in plasma was measured using a chromogenic substrate. It appeared that the measurement of heparin concentration in plasma was important in therapeutic control and evaluation of heparin. There was a correlation between the activated partial thromboplastin time (APTT) and heparin concentration in plasma, but since the gradients of regression line differed in each of the cases, measurement of APTT alone would give a different estimate of heparin concentration in each case. Fibrinopeptide A (FPA) is considered as the best indicator for evaluatin of therapeutic effects of heparin. Therapeutic heparin concentrations were defined as ranging from 0.2 to 1.2 IU/ml because the normalization of FPA was observed and there happened no hemorrhagic accidents in that range.