ABC | Volume 110, Nº1, January 2018

Original Article Soeiro et al Troponin vs. coronary lesion Arq Bras Cardiol. 2018; 110(1):68-73 Figure 1 – ROC curve identifying the sensitivity and the specificity of the best cutoff point of troponin as a discriminator of the probability of significant coronary lesion. AUC: area under the curve. ROC curve ROC curve ROC curve 1 – Specificity 1 – Specificity 1 – Specificity Sensitivity Sensitivity Sensitivity 1.0 0.8 0.6 0.4 0.2 0.0 1.0 0.8 0.6 0.4 0.2 0.0 1.0 0.8 0.6 0.4 0.2 0.0 Best cutoff point = 0.605 ng/dL: Sensitivity = 63.4% Specificity = 67% AUC = 0.685 Best cutoff point = 0.605 ng/dL: Sensitivity = 62.7% Specificity = 71% AUC = 0.703 Best cutoff point = 0.515 ng/dL: Sensitivity = 80.6% Specificity = 42% AUC = 0.608 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0 A – General population B – Without renal failure C – With renal failure Table 1 – Baseline characteristics and univariate analysis comparing patients with versus without significant coronary lesion Coronary lesions ≥ 70% p Present (N = 681) Absent (N = 310) Male sex (%) 72.10% 65.10% 0.018 # Age (median) 62.9 ± 11.30 63.9 ± 13.23 0.202 π Diabetes mellitus (%) 38.82% 40% 0.725 # Arterial hypertension (%) 79.30% 84.80% 0.038 # Chronic coronary disease (%) 13.70% 14.50% 0.724 # Dyslipidemia (%) 51.00% 50.00% 0.797 # FH of early CAD (%) 12.50% 10.60% 0.404 # Previous AMI (%) 39.70% 36.10% 0.284 # Smoking (%) 43.50% 31.30% < 0.0001 # Creatinine (mg/dL) (mean) 1.31 ± 1.20 1.32 ± 1.25 0.896* ST depression/T-wave inversion 36.30% 18.70% < 0.0001 # Troponin + / 99 th percentile 91.50% 72.60% < 0.0001 # Troponin + / Best cutoff point 63.40% 32.60% < 0.0001 # FH: family history; CAD: coronary artery disease; AMI: acute myocardial infarction; # : chi-square test; *: unpaired T test; π : Mann-Whitney U test. Discussion The results of this study in the Brazilian population are in accordance with those of recently published literature. Troponin positivity without association with coronary angiographic findings was observed in 31.3% of the patients. In addition, better specificity values were only achieved with a troponin cutoff point of 0.605 ng/dL, approximately 15 times the 99 th percentile of the method. When assessing the subgroup with renal failure, that level is even higher, hindering its correct interpretation. In a study published in 2012 derived from the Scottish Heart Health Extended Cohort , blood samples were collected and high-sensitivity troponin I levels were measured. The results showed that, in a population of 15340 individuals, 31.7% of the men and 18.1% of the women had high high-sensitivity troponin with no clinical manifestation at the time of blood collection, highlighting the problem of the specificity of the method. Positivity and worse prognosis were correlated in the long run (p < 0.0001), as reported in other studies. 4,10-12 That prevalence of troponin positivity not related to acute coronary artery disease is similar to that found in our study, although we assessed specifically patients with chest pain. Likewise, a prospective cohort study of 6304 patients with chest pain presenting to the emergency department has reported positive high-sensitivity troponin T in 39% of the cases diagnosed as non-coronary. 13 70