Prognostic value of electrocardiographic stress testing compared to thallium scintigraphy

The highly sensitive and specific thallium scintigraphy is compared to loading electrocardiography with regard to the two crucial parameters: loaded angina pectoris (AP) and horizontal or descendant depression of ST segment of 1.5 mm and deeper (ST). Effectiveness of loading ecg test was determined quantitatively in terms of sensitivity, specificity, prognostic value and test accuracy. Those criteria of positivity of the loading test showed that sensitivity was higher for AP than for ST (73% and 63%, resp.), but specificity was higher for ST (100%) than for AP (79%). The result of thallium test was estimated according to AP occurrence with 80% probability for positive prognosis and 70% probability for negative prognosis; with ST, probability of positive prognosis was 100% and that of negative prognosis was 69%. Test accuracy is 75% for AP and 79% for ST. The 100% probability of positivity of thallium scintigraphy in ST depressions of 1.5 mm and deeper discredits indication of this method in this cases. In the absence of ST depressions, the origin of typical pain during the loading ECG enhances probability of positivity of thallium scintigraphy more than twofold (53 vs. 21%).