title: Evaluating the role for the optical density in the diagnosis of heparin-induced thrombocytopenia following cardiac surgery.
abstract: The poor accuracy of the enzyme immune assay (EIA) contributes to the diagnostic challenge of heparin-induced thrombocytopenia (HIT) following cardiac surgery. We sought to determine if adjusting the threshold optical density (OD) defining a positive EIA improves the test's accuracy in subjects with an OD>0.40. We retrospectively analysed the results from both EIA and confirmatory serotonin release assays (SRAs) in cardiac surgery patients with EIA OD of >0.4. Employing the SRA as the standard, we compared the area under the receiver-operating characteristic (AUROC) curves of various OD measurements for identifying HIT. We examined baseline clinical variables associated with a positive SRA in the setting of a positive HIT EIA (OD >0.4). We then used logistic regression to identify baseline clinical variables independently associated with a positive SRA given a positive EIA. The cohort included 99 subjects with positive EIAs and 35% had positive SRAs. An OD>0.40 had moderate utility as a screening test for a positive SRA (AUROC: 0.68; 95% CI: 0.55-0.80). Increasing the OD threshold did not improve the HIT EIA's screening utility. Clinical variables independently associated with a positive SRA if the EIA were positive included female gender, absence of diabetes, and use of cardiopulmonary bypass. A relatively modest elevation in the OD measurement, when it is already known to be greater than 0.4, does not reliably exclude the potential for a positive SRA in this setting.
authors.affiliation: Washington Hospital Center, Washington, DC 20010, USA.
authors.forename: C M
authors.initials: CM
authors.lastname: Chan
authors.forename: P J
authors.initials: PJ
authors.lastname: Corso
authors.forename: X
authors.initials: X
authors.lastname: Sun
authors.forename: P C
authors.initials: PC
authors.lastname: Hill
authors.forename: A F
authors.initials: AF
authors.lastname: Shorr
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000906:Antibodies / Q000097:blood*; D000925:Anticoagulants / Q000009:adverse effects* / Q000276:immunology; D015415:Biomarkers / Q000097:blood; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism; D006348:Cardiac Surgical Procedures / Q000009:adverse effects*; D004219:District of Columbia; D005260:Female; D006493:Heparin / Q000009:adverse effects* / Q000276:immunology; D006801:Humans; D007124:Immunoenzyme Techniques; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D010978:Platelet Factor 4 / Q000276:immunology*; D011237:Predictive Value of Tests; D012372:ROC Curve; D012189:Retrospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D012701:Serotonin / Q000097:blood; D013921:Thrombocytopenia / Q000097:blood / Q000139:chemically induced / Q000175:diagnosis* / Q000276:immunology
chemical_list: D000906:Antibodies; D000925:Anticoagulants; D015415:Biomarkers; D012701:Serotonin; D010978:Platelet Factor 4; D006493:Heparin