A Comparative Study of Different Treadmill Scores to Diagnose Coronary Artery Disease Among Patients Attending Bangabandhu Sheikh Mujib Medical University

Introduction At present several treadmill scores have been proposed as means for improving the diagnostic accuracy of the exercise treadmill test (ETT) and to predict future risk of cardiac events (Berman et al., 1978 & Do et al., 1997). Although a large number of noninvasive stress testing modalities are currently available, the exercise ECG is still used as a standard for comparison with other clinical and testing risk markers. It is also the least costly of all provocative noninvasive tests. The Duke Treadmill Score (DTS), traditionally a prognostic score, was recently tested as a diagnostic score and shown to predict CAD better than the ST response alone(Shaw et al., 1998). But questions remain regarding the diagnostic accuracy of treadmill scores when applied to a different patient population; furthermore, many treadmill scores have not been compared with one another in the same population(Fearon et al., 2002).To date, no composite stress-test score or noninvasive risk index has been shown to provide both accurate diagnostic and prognostic risk estimates. Despite that exercise treadmill test remains a useful test for diagnosing coronary artery disease (CAD) in patients with chest pain and at intermediate risk for CAD (Do et al., 1997).The sensitivity and specificity of ETT varies considerably. According to a meta-analysis conducted by Gianrossi et al there was a wide variability in sensitivity and specificity of ETT [sensitivity 68± 16% (range 23-100%); specificity 77±17% (range: 17-100%). Another Meta analysis showed sensitivity of 81± 12% (range: 40-100%) and specificity of 66± 16% (range: 17-100%) (Myers et al., 1994).Fearon WF et al showed sensitivity and specificity was higher when treadmill scores were applied in comparison to ST response alone. They used a consensus score consisting of the Morise, Dentrano and VA score and found predictive accuracy of the consensus score for stratifying patients to low and high likelihood for CAD was significantly higher than the predictive accuracy of DTS, 80(74-86)% versus 71(65-77)% (p< 0.0001). But Fearon WF et al conducted the study only on male population in USA and the consensus score was calculated by average of computer generated treadmill scores. In 2012 Mao L et al have shown 73 out of 104 male patients were detected CAD both by ETT and CAG, the accuracy rate was 70.2% which was much higher than that (50.0%) of the female patients (p<0.05) and they only used ST changes alone to demonstrate ETT positivity In this study, we will compare the diagnostic accuracy of well known prognostic scores namely, Duke Treadmill Score, Simple Treadmill Score and Cleveland Clinic Score to identify significant coronary artery lesion in Bangladeshi male and female patients.

Rationale

Though exercise treadmill test has high false positive and negative rates(Zang et al., 2007) , it is cheap, easily available, less time consuming to the interpret results and its accuracy can be increased by calculating ST/HR index, treadmill score, QT dispersion and so on (Kronander 2010 &Dentrano 1989). On the contrary the gold standard test coronary angiogram for detecting CAD is expensive, time consuming, potentially hazardous with many complications and often the CAG shows normal coronary arteries in female population.ST-segment depression and chest pain as the classic criteria for CAD diagnosis are well known and accepted. Besides If treadmill score were used the diagnostic accuracy of ETT would had been higher. The accuracy of different treadmill scores in Bangladeshi population especially the female population is largely unknown. Duke Treadmill Score and Simple Treadmill Score are well validated score in western population and are used for diagnostic & prognostic interpretation of ETT. The predictive accuracy of DTS to diagnose CAD is 71% (Fearon 2002). In 2001 Raxwal V et al. showed simple treadmill score has sensitivity of 88% and specificity of 96%. If we calculate the accuracy of simple treadmill score using the formula "Accuracy = (Sensitivity) x Prevalence + (Specificity) x (1- Prevalence)" it sums up nearly 93% according to prevalence of CAD in urban population. Cleveland Clinic Score is a prognostic score of ETT. It gives value from which we can predict the probability of 3 year or 5 year survival. It was shown that it has a very high negative predictive value approaching 97%. Besides to the best of our knowledge Cleveland Clinic Score was not tested as a diagnostic predictor of CAD and there are few studies regarding treadmill scores predictability in Bangladesh. In our study we will use all of these three scores and compare their accuracy to predict significant CAD. DTS, Simplified Treadmill Score, and Cleveland clinic score can be implemented effectively to identify patients with low probability of CAD and excluded from undergoing expensive and potentially hazardous CAG if the real scenario of the treadmill scores is known in our population.

Research question

Howdo different treadmill scores (Duke Treadmill Score, Simple Treadmill Score, Cleveland Clinic Score) vary to predictability of Coronary Artery Disease in Bangladeshi population in a tertiary care hospital?