PLANAR TL-201 SCINTIGRAPHY IN ISCHEMIC-HEART-DISEASE - A CRITICAL REEVALUATION OF QUALITATIVE AND QUANTITATIVE DATA-ANALYSIS

The aims of the present study were to examine the observer agreement o f qualitative (visual) and quantitative (computer-assisted) analysis o f planar Tl-201 imaging and to compare the diagnostic values of these methods in the detection of infarcted and exercise-induced ischaemic m yocardium. The study population comprised of 119 patients (aged 24-77 years) referred consecutively for stress thallium scintigraphy for eit her diagnostic reasons (n=42, 35%) or for further evaluation of known coronary artery disease (CAD) (n=77, 65%). The interobserver agreement was low with the qualitative method and significantly higher with the quantitative method: Kappa-values 0.29-0.39 vs. 0.80-0.92, P<0.00001. Sensitivity and specificity for the detection of previous Q-wave infa rct was significantly higher with the quantitative method (94% and 94% ) compared to the qualitative method (77% and 74%), P<0.01. The corres ponding predictive values of a positive and a negative test were 96% a nd 92% vs. 80% and 70% (P<0.01). In 86 patients in whom coronary angio graphy was performed the two methods did not differ significantly rega rding sensitivity, specificity and predictive values for the diagnosis of reversible ischaemia or rather CAD. However, when 22 patients with a maximal exercise heart rate <80% of the predicted target heart rate were excluded the sensitivity was increased with both techniques and was significantly higher with the quantitative method. We conclude tha t qualitative image analysis has an unacceptably low reproducibility a nd that quantitative image analysis increases the diagnostic value of Tl-201 scintigraphy considerably in both the detection of previous inf arcts and, provided a sufficient exercise level is achieved, in the di sclosure of reversible myocardial ischaemia.