Autoantibodies against apolipoprotein A‐1 and phosphorylcholine for diagnosis of non‐ST‐segment elevation myocardial infarction

Abstract

To explore the diagnostic accuracies of anti-apolipoproteinA-1 (anti-ApoA-1) IgG and anti-phosphorylcholine (anti-PC) IgM alone, expressed as a ratio (anti-ApoA-1 IgG/anti-PC IgM), and combined with the Thrombolysis In Myocardial Infarction (TIMI) score for non-ST-segment elevation myocardial infarction (NSTEMI) (NSTEMI-TIMI score) to create a new diagnostic algorithm - the Clinical Autoantibody Ratio (CABR) score - for the diagnosis of NSTEMI and subsequent cardiac troponin I (cTnI) elevation in patients with acute chest pain (ACP). In this single-centre prospective study, 138 patients presented at the emergency department with ACP without ST-segment elevation myocardial infarction. Anti-ApoA-1 IgG and anti-PC IgM were assessed by enzyme-linked immunosorbent assay on admission. Post hoc determination of the CABR score cut-off was performed by receiver operating characteristics analyses. The adjudicated final diagnosis was NSTEMI in 17% (24/138) of patients. Both autoantibodies alone were found to be significant predictors of NSTEMI diagnosis, but the CABR score had the best diagnostic accuracy [area under the curve (AUC): 0.88; 95% confidence interval (CI): 0.82-0.95]. At the optimal cut-off of 3.3, the CABR score negative predictive value (NPV) was 97% (95% CI: 90-99). Logistic regression analysis showed that a CABR score >3.3 increased the risk of subsequent NSTEMI diagnosis 19-fold (odds ratio: 18.7; 95% CI: 5.2-67.3). For subsequent cTnI positivity, only anti-ApoA-1 IgG and CABR score displayed adequate predictive accuracies with AUCs of 0.80 (95% CI: 0.68-0.91) and 0.82 (95% CI: 0.70-0.94), respectively; the NPVs were 95% (95% CI: 90-98) and 99% (95% CI: 94-100), respectively. The CABR score, derived from adding the anti-ApoA-1 IgG/anti-PC IgM ratio to the NSTEMI-TIMI score, could be a useful measure to rule out NSTEMI in patients presenting with ACP at the emergency department without electrocardiographic changes.