Prevalence of heparin in samples submitted for lupus anticoagulant testing.

Abstract

Introduction: Lupus anticoagulant (LA) testing can be affected by the presence of anticoagulant medications such as heparin, and current guidelines recommend caution when performing and interpreting LA testing for patients who are receiving anticoagulation treatment. We searched our reference laboratory database to determine the prevalence of heparin in samples submitted for LA testing.

Methods: We reviewed 18,676 LA reflexive testing panels. Heparin was identified by partial thromboplastin time (before and after heparin neutralization), thrombin time, and reptilase time results. Samples containing heparin were subclassified (not significant, significant) according to the degree of thrombin time prolongation.

Results: Of the panels, 1909 panels (10%) were LA positive. We found that 2011 samples (11%) contained some heparin and that 616 samples contained a significant amount of heparin (3% of all samples and 31% of samples containing heparin). LA-positive results were obtained for 80 (13%) of these samples, which represented 4% of the samples containing heparin and 0.4% of all samples.

Conclusion: LA-testing guidelines recommend that samples not contain anticoagulant medications. Despite these recommendations, our data show that a significant proportion (11%) of these samples contain heparin. We conclude that LA-testing algorithms should use methods to identify and neutralize heparin and that laboratories should provide education regarding appropriate sample collection for LA testing.