Diagnostic accuracy of myocardial perfusion imaging in a study population without post-test referral bias

Most previous studies on the accuracy of myocardial perfusion imaging (MPI) are hampered by post-test referral bias, in that referral for coronary angiography was influenced by the MPI result. In this way, patients with a normal MPI result less frequently underwent catheterization, a tendency supposed to cause an underestimation of test specificity and an overestimation of test sensitivity. MPI by use of a gated dual-isotope protocol was undertaken before angiography in 357 patients referred for angiography for suspected stable angina pectoris. The MPI reports were kept secret to prevent post-test referral bias. The MPI study was normal in 215 patients (60%) and showed reversible perfusion abnormalities in 118 (33%) and fixed defects in 24 (7%). Angiography was normal in 231 patients (65%) and revealed 1 or more significant stenoses in 126 (35%). With angiography as the reference, the sensitivity and specificity of MPI for detecting significant coronary artery stenosis were 75% and 79%, respectively. In this prospective study without post-test referral bias, we found a lower sensitivity and slightly higher specificity than in studies with post-test referral bias. The imperfect accuracy may reflect differences between anatomic and physiologic imaging.