Determination of heparin levels in blood with activated partial thromboplastin time by a piezoelectric quartz crystal sensor

A piezoelectric quartz crystal (PQC) sensor, possessing a sensitive frequency response to viscoelastic variations of substance loading on an electrode surface, was used to determine both whole blood activated partial thromboplastin time (WBaPTT) and plasma activated partial thromboplastin time (PLaPTT) induced by anticoagulant heparin. The PQC sensor results showed a linear relationship between WBaPTT (or PLaPTT) and heparin levels in clinically relevant concentrations (0-0.4 unit/ml). Mean of individual R-2 (= 0.9491) for a regressive curve between WBaPTT and heparin concentrations was adequately shown. The PQC method can be used to evaluate the effect of heparin through determination of WBaPTT owing to comparable sensitivity (P < 0.01) with that of aPTT by optical coagulometry (OCaPTT). Furthermore, we found the results of WBaPTT with various heparin concentrations (n = 9) to be well correlated with those of OCaPTT (correlation coefficient = 0.9441). Linear calibration plots were extended into 3 units/ml of heparin in PLaPTT and WBaPTT. It was suggested that the PQC method will provide a more convenient operation, may be useful in clinical situations for rapid monitoring heparin therapy using small volume (20 l) of whole blood specimens. (C) 2001 Elsevier Science B.V. All rights reserved.