Abstract 725: Effect of Referral Bias on the Diagnostic Accuracy of N-13 Ammonia and Rubidium-82 Myocardial Perfusion Imaging with Positron Emission Tomography in the Detection of Coronary Artery Disease
Objectives: Few studies have evaluated the accuracy of positron emission tomography (PET) myocardial perfusion imaging (MPI) for the detection of angiographic coronary artery disease (CAD) in the contemporary era. Prior studies were limited by including patients with known CAD and none assessed the influence of referral bias on diagnostic accuracy. Our primary objective was to assess the accuracy of PET MPI with rubidium (Rb)-82 and N-13 ammonia (NH3) for diagnosis of angiographic CAD in patients without known CAD, corrected for referral bias. Secondary objectives were to evaluate diagnostic performance in females and obese patients.
Methods: Between 2000 to 2006, 883 PET MPI studies were performed. A total of 122 patients (48 [NH3], 74 Rb-82) without known CAD on coronary angiography (CA) within 3 months after PET MPI were included. Significant angiographic CAD was defined per Coronary Artery Surgery Study criteria. PET MPI images were interpreted using the 17-segment model and a 5-point scale (0=normal, 4 = absent uptake). A summed stress score of ≤1 was considered abnormal. Results were adjusted for referral bias using 2 different formulas (Diamond vs. Begg and Greenes).
Results: Mean age was 57±11 years, 47% were women, and 100 patients were obese (mean BMI 36±8). The majority of patients (78%) who underwent CA had abnormal PET MPI. Unadjusted and adjusted test performance for both Rb-82 and NH3 PET MPI are shown in Table 1⇓. Unadjusted sensitivity was 96% and specificity 34% for the whole group. Adjustment for referral bias considerably decreased sensitivity and increased specificity (Table 1⇓).
Conclusions: Unadjusted indices for PET MPI demonstrate high values for sensitivity and low values for specificity. Adjustment for referral bias results in lower sensitivity and higher specificity. Overall, PET MPI with NH3 was more sensitive and Rb-82 was more specific for detection of CAD. Obesity and female gender had only slightly different test performance.