Spss statistical software v 15

Statistical analyses and graphs were performed by SPSS statistical software v. 15.0 (SPSS Inc., Chicago, IL, USA) and R software v. 2.15.1 (R Foundation for Statistical Computing). Differences between groups were estimated by non-parametric Kruskal-Wallis (with Bonferroni correction for multiple comparisons) or Mann-Whitney tests. Differences in proportions were estimated by Chi-squared or Fisher’s exact test. Confidence intervals (CI) were calculated using CIA software v. 2.1.1 (by T Bryant, University of Southampton, UK). Distribution of basal and subsequent cTnI data, assessed by the Kolmogorov–Smirnov and the Shapiro-Wilk tests, and visually by histogram and kernel density plot, was found to be highly skewed. Predictors for positive cTnI test (> 40 ng/L) were estimated by univariate and multivariate logistic regression. Sensitivity (Se), specificity (Sp), positive predictive value (PPV) and negative predictive value (NPV) to detect “unequivocal ACS” were calculated in the whole sample and in three subgroups (see column 1 in Table 2) and were provided with their 95% confidence intervals, according to the efficient-score method (corrected for continuity).