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Figure 3 Illustration of the power of the NI to rule in (a) or rule out (b) angiographic three-vessel and/or left main disease. Posttest probabilities of disease could not be calculated at the extreme ends of the noninvasive index, because sensitivities and specificities regarding the detection of angiographic three-vessel and/or left main disease were 100%. (a) The noninvasive index is represented on the X-axis and the posttest probability of severe angiographic disease after a positive test result on the Y-axis ((+)PTPD). The solid horizontal line represents the pretest probability of severe angiographic disease, i.e., 23%. Increasing values of the NI enhance the probability of severe angiographic disease (posttest) to levels above 65–70% (arrow). (b) The NI is represented on the X-axis and the posttest probability of no severe angiographic disease after a negative test result on the Y-axis ((–)PTPN). The solid horizontal line represents the pretest probability of no severe angiographic disease, i.e., 77%. Decreasing values of the NI enhance the probability of no severe angiographic disease (posttest) to levels above 95% (arrow).