To assess the impact of heparin lot on the correlation between heparin concentration and activated partial thromboplastin time (aPTT), the aPTT therapeutic range, and the heparin level.
Retrospective analysis of data from 2 previous studies.
Teaching institution with 929 beds.
Ninety-five patients receiving heparin with 5 different lots (study 1) and 35 patients receiving heparin with 3 different lots (study 2).
Laboratory-based aPTT and heparin level by anti-factor Xa analysis. Standard heparin curves were created for each lot. Each patient's heparin level was determined off each standard curve.
Correlations between heparin concentration and aPTT ranged from 0.87 to 0.89 (study 1) and 0.86 to 0.87 (study 2). Slopes of regression lines were not significantly different. Therapeutic ranges generated from lot-specific heparin levels were similar. Average bias in heparin levels from varying lots ranged from 0.005 to 0.036 units/mL.
The recommendation to reevaluate the aPTT therapeutic range with each new lot of heparin requires further evaluation.