Investigation of the effect of high sensitivity troponin T variability in normal limits on exercise test positivity and coronary anatomy

Aim of the study: High sensitivity troponins; are the gold standard tests used in diagnosis of myocardial infarction and whose prognostic values are also shown in many studies.However there is no recommendation for the use of these tests in current guidelines for the management of patients with chronic coronary artery disease (CCAD). In this study, we examined the impacts of changes in the normal range of hsTnT levels, which were examined before exercise stress test in the patients with suspected CCAD, had pre-test probability in the middle risk class and who were not previously diagnosed with CCAD, on the test positivity results. Henceforth, patients who have positive test results are taken into coronary angiography procedure due to natural course. Therefore, coronary artery anatomy was also evaluated. Material and Methods: In our study, we included 218 patients who applied to Istanbul Medical Faculty Cardiology Department and Emergency Internal Medicine Polyclinic between April 2018-December 2019. Our patients had suspected CCAD and their pretest probability were in middle risk class. hsTnT values were sent from the patients at the time of admission and hsTnT levels were studied with the Cobas E411 device from the samples taken from the peripheral vein using the Elecsys method. Exercise stress test was performed according to the Standard Bruce Protocol with the Philipss Stress Vue Device in the laboratory of our hospital for the patients whose hsTnT levels were detected within the normal range. Coronary angiography was performed in patients with positive stress test due to the natural course of the disease, and therefore coronary angiography results were also examined from the patient medical papers. Severity of the coronary artery disease (CAD) was determined using the Gensini Scoring System and more than %50 stenosis in the coronary artery was considered as a significant stenosis. Results: There were 218 patients in our study. Test results of 26 patients were positive, while 192 patients' test results were negative. Patients were divided into two groups according to the limit value of 6.32 pg / ml hsTnT obtained by ROC analysis. As a result of the analysis, the age (p:0,001), systolic blood pressure (p:0,008), height (p:0,043) and body-mass index (p:0,004) of the patients with hsTnT results higher than 6.32 pg/ml were statistically significantly higher than the other group. As a result of ROC analysis for hsTnT, it was determined that the value of 6.32 pg/mL that was predictive for test positivity with 54% sensitivity and 70% specificity. While the effort test of 72 patients with a hsTnT value> 6.32 pg / ml was positive in 19 (19.4%); on the other hand the effort test was positive in 12 (8.2%) of 146 patients with a TnT value of 6.32 pg/mL (p: 0.029). The relationship between hsTnT level and Gencini Score was evaluated by Pearson and / or Spearman correlation analysis. Highly positive correlation was found between hsTnT level and Gensini Score (Gensini Score r: 0.841 / p <0.001). In order to predict significant coronary artery stenosis, the specificity and sensitivity of hsTnT was evaluated by ROC analysis, and it was determined that the value of 6.5 pg/mL hsTnT predicted the presence of significant coronary artery stenosis with 88% sensitivity and 85% specificity. The hsTnT values of patients with and without significant stenosis in the coronary arteries were compared with the Mann Whitney U test. The mean of hsTnT values of 9 patients with significant stenosis in the coronary arteries was 8.82.3 pg/mL, and the mean of hsTnT values of 13 patients without coronary arteries was 4.52.1 pg/mL. The difference was statistically significant (p: 0.001). The relationship between hsTnT and Duke Treadmill Score was evaluated with the Spearman rho method. Patients with hsTnT value> 6.32 pg/lt were found to have a higher Duke Treadmill Score, but the correlation was weak (p: 0.001 r: 0.21). The mean hsTnT values of patients with positive and negative effort tests were compared with the Student T test, and the mean value was mathematically higher in the positive group, but it was statistically insignificant (p: 0.15). Conclusion: According to the data of our study, hsTnT levels in normal limits; it predicts test positivity with a sensitivity of 54% and 70% specificity over the limit value of 6.32 pg / ml in patients with a suspicion of CCAD, who has not previously been diagnosed with CAD, and whose pre-test probability is in the middle risk class, and above this limit value; test positivity is significantly higher. In addition, patients with a hsTnT value above this limit value had a significantly higher DTS value, and hence the hsTnT level examined before the test; while increasing the sensitivity of the stress test, it also gives clues about the prognosis of the patients as it is correlated with DTS. As the hsTnT value increases, the Gensini Score increases and the relationship between them was statistically significant and their correlations were close to perfect. When the hsTnT value increases, the probability of significant stenosis in the coronary arteries also increases, and this increase was statistically significant. The hsTnT value, which examines before the effort test, increases not only the sensitivity but also the specificity of the test. As a result; the hsTnT levels, that examines before the effort test, increase the sensitivity and specificity of the test, as well as can provide valuable information about the prognosis of the patients. Current guidelines recommend evaluating at complete blood count, kidney function tests, and lipid profile levels if CCAD is suspected. Therefore, it is reasonable and plausible to evaluate the hsTnT levels of the patients besides all these tests. Keywords: High sensitivity troponin T, stress test, Gensini Score, Duke Treadmill Score