Background:

We evaluated if risk scores commonly used to predict the absence
of significant stenosis at coronary computed tomography (CT) angiography
are useful to predict a normal stress myocardial perfusion imaging
(MPI) study.

Methods:

Our cohort included a total of 1422 consecutive patients with zero coronary artery calcium score (ZCS) who underwent
⁸²
Rb
PET/CT for evaluation of suspected coronary artery disease (CAD).
Predictive models were constructed as reported by Genders et al. and
Alshahrani et al., and the probability of abnormal summed stress score
(SSS) and of reduced myocardial perfusion reserve (MPR) based on these
risk scores was assessed.

Results:

In the overall population, the prevalence of abnormal SSS was 0.10
and the prevalence of reduced MPR was 0.17 (both P < .001).The
observed frequencies of abnormal SSS and reduced MPR vs the
probabilities predicted by the Genders and Alshahrani models were above
the diagonal identity line, highlighting an underestimation of the
observed occurrence by these models. The areas under the receiver
operating characteristic curve of the Genders and Alshahrani models
indicated lack of discriminative ability for predicting abnormal SSS
(0.547 and 0.527) and reduced MPR (0.509 and 0.538). The Hosmer-Lemeshow
test revealed that both models underestimated the observed occurrence
of abnormal SSS and reduced MPR.

Conclusions:

Available models were unable to identify among patients with ZCS
those with a low probability of a normal stress MPI study. Thus, an
optimal approach to rule out from MPI patients without detectable
coronary calcium still needs to be improved.