SENSITIVITY AND SPECIFICITY OF THE HEMOCHRON, HEMOTEC AND APTT FOR THE DETECTION OF LOW CONCENTRATIONS OF HEPARIN

This study compared two bedside methods recommended for the detection of low concentrations of heparin and the activated partial thromboplas tin time (APTT), with reference to a laboratory measure of heparin con centration. Patients undergoing cardiopulmonary bypass had blood drawn at four stages when low levels of heparin could be expected. At each stage four tests were performed: whole blood clotting time using a Hem ochron analyser with a Saline-Rinsed test cartridge, whole blood clott ing time using a Hemotec analyser with a High Range Heparinase test ca rtridge, APTT; and heparin concentration by polybrene neutralization. Thirty patients were studied. The sensitivity of the Saline-Rinsed Hem ochron, Hemotec High Range Heparinase, and APTT in detecting concentra tions of heparin less than I U/ml was 38%, 40% and 97%, respectively, while specificities were 87%, 90%, and 30%, respectively. Neither the Saline Rinsed Hemochron, nor the Hemotec Heparinase cartridge reliably detected concentrations of heparin less than I U/ml.