Heparin contamination in coagulation testing and a protocol to avoid it and the risk of inappropriate FFP transfusion.

Artifactual heparin contamination of blood samples drawn for coagulation testing is an ongoing problem. A retrospective analysis of activated partial thromboplastin times (APTTs) greater than 45 seconds from patients on neither heparin nor Coumadin (Dupont, Wilmington, DE) therapy shows complete correction of the APTT to normal in 39% of such samples after treatment with heparinase. Recheck of samples with significantly prolonged APTTs after treatment with heparinase is proposed as the best method to avoid inappropriate transfusion of fresh frozen plasma.