Sensitivity, specificity and predictive accuracy of Q wave, QX/QT ratio, QTc interval and ST depression during exercise testing in men with coronary artery disease.

One hundred forty-three subjects (107 with coronary artery disease [CAD], 23 without CAD [evaluated by coronary angiography] and 13 athletes) were selected for this study. All subjects underwent exercise testing to evaluate sensitivity, specificity and predictive value of Q wave, QX/QT ratio, QTc interval and ST depression. The Q-wave analysis revealed less sensitivity (49%) and less specificity (83%) than ST depression (71% and 97%, respectively). The QTc criterion had greater sensitivity (80%) than ST depression but less specificity (11%). The QX/QT criterion was no different in sensitivity (74%) but had less specificity (69%). To establish the statistical evaluation of the positive predictive value in CAD, variations in the prevalence of the disease were considered. A 90% prevalence gives the best positive predictive value on all evaluated measurements, between 100% for ST depression and 89% for the QTc criterion. A 5% prevalence, however, gives an acceptable positive predictive value only on ST-segment depression (57%).