Routine use of chest x-ray for low-risk patients undergoing a periodic health examination: a retrospective cohort study.

Background: Many evidence-based recommendations advocate against the use of routine chest x-rays for asymptomatic, low-risk outpatients; however, it is unclear how regularly chest x-rays are ordered in primary care. Our study aims to describe the frequency of, and variation in, routine chest x-ray use in low-risk outpatients among primary care physicians.

Methods: In this retrospective cohort study, Ontario residents aged 18 years and older with a periodic health examination (PHE) between Apr. 1, 2010, and Mar. 31, 2015, were identified via administrative claims data. Patients with a recent history (last 3 years) of any of the following were excluded: cardiac or pulmonary disease, high-risk comorbidity (e.g., diabetes), consultations/visits or procedures involving cardiac or pulmonary specialists, cancer and severe chest trauma. The primary outcome, a routine chest x-ray, was defined as at least 1 chest x-ray claim within 7 days after a PHE.

Results: While a routine chest x-ray followed only 2.42% of 2 847 508 PHEs, one-quarter of family physicians (499/2031) ordered chest x-rays for more than 5.0% of their PHEs (interquartile range 1.5%-5.0%) and accounted for 62.9% of all tests observed. Routine chest x-ray use declined by 2.0% per quarter (adjusted rate ratio 0.98, 95% confidence interval [CI] 0.97-0.98). Older age (45-64 yr v. 18-44 yr, adjusted odds ratio [OR] 1.82, 95% CI 1.78-1.86; ≥ 65 yr v. 18-44 yr, adjusted OR 2.48, 95% CI 2.39-2.58) and male sex of the patient (OR 2.19, 95% CI 2.14-2.24) and male sex of the provider (OR 1.55, 95% CI 1.51-1.59) were significantly associated with increased odds of a routine chest x-ray being ordered.

Interpretation: It is relatively uncommon for a chest x-ray to be ordered as part of a PHE in Ontario; however, the substantial variation observed among physicians suggests potential for interventions targeted at the most frequent users.