Evaluation of the TAS analyzer and the low-range heparin management test in patients undergoing extracorporeal membrane oxygenation

Background: The new Low-Range Heparin Management Test (LHMT), a method for point-of-care testing (POCT) of heparinization, has been designed to functi on at the low to moderate heparin concentrations typically found in patient s undergoing extracorporeal membrane oxygenation (ECMO). In this study, the new method is compared with two POCT methods and a laboratory-based anti-X a assay. Methods: We obtained 760 whole blood samples from 13 patients undergoing EC R IO. All samples were tested immediately by the LHMT, the Activated Clotti ng Time (ACT) test, and its low-range counterpart (ACT-LR). Aliquots from t he same blood draw were frozen for later anti-Xa analysis using the Diagnos tica Stags method on the Roche Cobas Fara-II, Results: The precision was best for duplicate citrated LHMT samples (CV = 3 .1%). LHMT clotting limes (overall median, 162 s) were typically shorter th an ACT or ACT-LR times (247 and 235 s, respectively). The relationship betw een the LHMT and the other POCT methods differed significantly from patient to patient (P <0.0001), and a meaningful single relationship between the m ethods could not he obtained. The overall correlation coefficient between c lotting time values and actual heparin concentrations was less than or equa l to0.48 for each of the instruments tested, although time plots of each an alyzer's data suggested that they detected heparin dosage changes within si ngle patients. Conclusions: The performance of the LHMT on the TAS Analyzer is equivalent to that of currently commercially available POCT methods. The lack of agree ment between absolute clotting time values and heparin concentrations sugge sts the need for reexamination of current ECR IO patient management strateg y. (C) 2001 American Association for Clinical Chemistry.