The power of zero calcium in 82-Rubidium PET irrespective of sex and age.

BACKGROUND: Despite clinical suspicion, many non-invasive tests for coronary artery disease (CAD) are normal. Coronary artery calcification score (CACS) is a well-validated method to detect and risk stratify CAD. Patients with zero calcium score (ZCS) rarely have abnormal tests. Therefore, aims were to evaluate CACS as a gatekeeper to further functional downstream testing for CAD and estimate potential radiation and cost savings.

METHODS: Consecutive patients with suspected CAD referred for PET were included (n = 2640). Prevalence and test characteristics of ZCS were calculated in different groups. Summed stress score ≥ 4 was considered abnormal and summed difference score ≥ 7 equivalent to ≥ 10% ischemia. To estimate potential radiation/cost reduction, PET scans were hypothetically omitted in ZCS patients.

RESULTS: Mean age was 65 ± 11 years, 46% were female. 21% scans were abnormal and 26% of patients had ZCS. CACS was higher in abnormal PET (median 561 vs 27, P < 0.001). Abnormal PET was significantly less frequent in ZCS patients (2.6% vs 27.6%, P < 0.001). Sensitivity/negative predictive value (NPV) of ZCS to detect/exclude abnormal PET and ≥ 10% ischemia were 96.8% (95%-CI 95.0%-97.9%)/97.4% (95.9%-98.3%) and 98.9% (96.7%-99.6%)/99.6% (98.7%-99.9%), respectively. Radiation and cost reduction were estimated to be 23% and 22%, respectively.

CONCLUSIONS: ZCS is frequent, and most often consistent with normal PET scans. ZCS offers an excellent NPV to exclude an abnormal PET and ≥ 10% ischemia across different gender and age groups. CACS is a suitable gatekeeper before advanced cardiac imaging, and potential radiation/cost savings are substantial. However, further studies including safety endpoints are needed.