Clinical question: How useful are rapid immunoassays (RIs) compared to other tests for heparin-induced thrombocytopenia (HIT)?
Background: HIT is a clinicopathologic diagnosis, which traditionally requires clinical criteria and laboratory confirmation through initial testing with enzyme-linked immunosorbent assay (ELISA) and “gold standard” testing with washed platelet functional assays when available. There are an increasing number of RIs available, which have lab turnaround times of less than one hour. Their clinical utility is not well understood.
Study design: Meta-analysis.
Setting: Twenty-three studies.
Synopsis: The authors found 23 articles to include for review. These studies included 5,637 unique patients and included heterogeneous (medical, surgical, non-ICU) populations. These articles examined six different rapid immunoassays, which have been developed in recent years. All RIs examined had excellent negative predictive values (NPVs) ranging from 0.99 to 1.00, though positive predictive values (PPVs) had much wider variation (0.42–0.71). The greatest limitation in this meta-analysis is that 17 of the studies were marked as “high risk of bias” because they did not compare the RIs to the “gold standard” assay.
Bottom line: RIs for the diagnosis of HIT have very high NPVs and may be usefully incorporated into the diagnostic algorithm for HIT, but they cannot take the place of “gold standard” washed platelet functional assays.
Citation: Sun L, Gimotty PA, Lakshmanan S, Cuker A. Diagnostic accuracy of rapid immunoassays for heparin-induced thrombocytopenia: a systematic review and meta-analysis [published online ahead of print January 14, 2016]. Thromb Haemost. doi:10.1160/TH15-06-0523.