• Amjed Kadhim-Saleh, James C Worrall, Monica Taljaard, Mathieu Gatien, and Jeffrey J Perry.
• *Faculty of Medicine,Public Health and Preventive Medicine,University of Ottawa,ON.
• Can J Emerg Med. 2018 Mar 1; 20 (2): 275-283.

ObjectivesPhysician variation in the use of computed tomography (CT) is concerning due to the risks of ionizing radiation, cost, and downstream effects of unnecessary testing. The objectives of this study were to describe variation in CT-ordering rates among emergency physicians (EPs), to measure correlation between perceived and actual CT-ordering rates, to assess attitudes that influence decisions to order imaging tests, and to identify EP attitudes associated with higher CT utilization.MethodsThis study was a retrospective review of imaging and administrative billing records at two emergency department sites of a tertiary care adult teaching hospital. The study also included a cross-sectional survey of EPs at this hospital. We asked physicians about their perceived ordering behaviour, and what factors influenced their decision to order a CT. We examined correlations between perceived and actual CT-ordering rates. We adjusted ordering rates for shift distribution using a logistic regression model and identified outlier physicians whose ordering rate was significantly lower or higher than expected. We used multivariable regression analysis to determine which survey responses predicted higher CT utilization.ResultsDuring the study period, 59 EPs saw 45,854 patients, and ordered 6,609 CTs - a mean ordering rate of 14.4% (standard deviation (SD)=4.3%). The ordering rate for individual physicians ranged from 5.9% to 25.9%. Of the 59 EPs, 13 EPs were low-ordering outliers; 12 were high-ordering outliers. Forty-five EPs (76.3%) completed the survey. Mean perceived ordering rate was 12.6%, and was weakly correlated with actual ordering (r=0.19, p=0.21). 42 EPs (93.3%) believed they ordered "about the same" or "fewer" CTs than their peers. Of the 17 EPs in the two highest ordering quintiles, only 3 (18%) knew they were high orderers. In the multivariable analysis, higher ordering was associated with increasing strength of response to the following predictors: medico-legal risk (relative risk [RR]=1.18, 95% CI: 1.03-1.21), risk of contrast (RR=1.14, 95% CI: 1.07-1.22), what colleagues would do (RR=1.09, 95% CI: 0.99-1.19), risk of missing a diagnosis (RR=1.08, 95% CI: 0.98-1.21), and patient wishes (RR=1.07, 95% CI: 0.97-1.17).ConclusionsThere is large variation in CT ordering among EPs. Physicians' self-reported ordering rate correlates poorly with actual ordering. High CT orderers were rarely aware that they ordered more than their colleagues. Higher rates of ordering were observed among physicians who reported increased concern with 1) risk of missing a diagnosis, 2) medico-legal risk, 3) risk of contrast, 4) patient wishes, and 5) what colleagues would do.

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