Table 1.
Frequency of thrombocytopenia (>50% platelet count decrease) among EIA+ patients (polyspecific or IgG-specific assay) who received heparin (unfractionated or low-molecular-weight): a comparison of SRA+ versus SRA− status
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Frequency of thrombocytopenia (>50% platelet count decrease) among EIA+ patients (polyspecific or IgG-specific assay) who received heparin (unfractionated or low-molecular-weight): a comparison of SRA+ versus SRA− status

The data are consistent with the SRA having a high sensitivity for HIT (> 95%); the specificity of the SRA depends on the clinical situation, but in most circumstances is at least 90%. Patients in studies “A” and “B” were tested in both the polyspecific and IgG-specific assays. Data used to construct this table were obtained from the published literature.3,19–21 

NA indicates not available.

*For the data shown, the cutoff for a positive SRA was 20% serotonin release. For study A (post-orthopedic surgery), if instead a 50% serotonin-release cutoff is used, the comparisons (polyspecific EIA) yield similar results: 11 of 20 versus 1 of 62 (P < .0001), and unchanged data for study B (VTE patients).

†For the VTE study, EIA results were ≥ 1.0 units of OD.

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