Accurate, noninvasive evaluation for obstructive coronary artery disease (CAD) remains challenging and inefficient. In this study, 171 patients presenting with stable chest pain and related symptoms without a history of CAD were referred to 6 cardiologists for evaluation. In the prospective cohort of 88 patients, the cardiologist's diagnostic strategy was evaluated before and after gene expression score (GES) testing. The GES is a validated, quantitative blood-based diagnostic test measuring peripheral blood cell expression levels of 23 genes to determine the likelihood of obstructive CAD (at least 1 vessel with ≥ 50% angiographic coronary artery stenosis). The objective of the study was to measure the effect of the GES on diagnostic testing using a pre/post study design. There were 83 prospective patients evaluable for study analysis, which included 57 (69%) women, mean age 53 ± 11 years, and mean GES 12.5 ± 9. Presenting symptoms were classified as typical angina, atypical angina, and noncardiac chest pain in 33%, 60%, and 7% of patients (n = 27, 50, and 6), respectively. After GES, changes in diagnostic testing occurred in 58% of patients (n = 48, P < 0.001). Of note, 91% (29/32) of patients with decreased testing had low GES (≤ 15), whereas 100% (16/16) of patients with increased testing had elevated GES (P < 0.001). A historical cohort of 83 patients, matched to the prospective cohort by clinical factors, had higher diagnostic test use compared with the post-GES prospective cohort (P < 0.001). In summary, the GES showed clinical utility in the evaluation of patients with suspected obstructive CAD presenting to the cardiologist's office.