Added value of coronary artery calcium score in the reporting of SPECT versus PET myocardial perfusion imaging

Background Knowledge of coronary artery calcium score (CACS) influences the interpretation of myocardial perfusion imaging (MPI) with SPECT; however, the impact on PET interpretation remains unclear. We compared the added value of CACS to reporting MPI using SPECT vs PET. Methods We retrospectively included 412 patients. 206 patients who underwent Rb-82 PET were propensity-based matched to a cohort of 4018 patients who underwent cadmium-zinc-telluride SPECT MPI to obtain a comparable group of 206 SPECT patients. Next, we created four image sets: SPECT MPI-only, PET-only, SPECT + CACS, and PET + CACS. Two physicians interpreted the 824 images as normal, equivocal, or abnormal for ischemia or irreversible defects. Additionally, event rates were compared between PET and SPECT groups during 30-month follow-up. Results PET yielded more scans interpreted as normal than SPECT (88% vs 80%, respectively, P = 0.015). Adding CACS to SPECT increased the percentage of normal scans to 86% (P = 0.014), whereas this effect was absent for PET (90%, P = 0.77). Annualized event rates for images interpreted as normal did not differ and varied between 0.7 and 2.0% (P > 0.084). Conclusion Adding CACS correctly increased the percentage of normal scans for SPECT MPI but not for PET, possibly limiting the effect of adding CACS to reporting PET.