Abstract
This study examines interphysician variability of diagnostic yield in computed tomographic pulmonary angiogram for pulmonary emboli.
Pulmonary embolism (PE) can be life-threatening and, when suspected, is usually investigated by computed tomographic pulmonary angiogram (CTPA). Concerns related to overutilization and harmful ionizing radiation have identified CTPA as an area in need of resource stewardship. The purpose of this study was to explore interphysician variability in CTPA diagnostic yield and to identify any associated physician characteristics that could inform an intervention to reduce overuse in our institution.
Methods
We retrospectively reviewed all CTPAs at an academic teaching hospital in Montreal, Quebec, Canada, from September 2014 to January 2016. Studies were classified as positive or negative; indeterminate examinations, and those performed for chronic pulmonary emboli were excluded. A total of 1394 examinations ordered by 182 physicians were included, of which 199 (14.3%) were positive and 1195 (85.7%) were negative. A multivariable logistic regression analysis was performed to explore whether physician specialty, years in practice, physician sex, or total numbers of studies ordered per physician were associated with CTPA diagnostic yield. We used a generalized estimating equations (GEE) approach to account for patients who underwent repeated examinations over the study period. Statistical tests of hypothesis were 2-sided with a significance of P ≤ .05. All analyses were performed using SAS statistical software (version 9.4, SAS Institute Inc). The McGill University Health Centre research ethics board approved this study.
Results
According to our analysis using GEE logistic regression, the odds of a positive CTPA decreased as the total number of scans ordered per physician increased (Table). For each additional 10 studies ordered, the odds of a positive result decreased (odds ratio [OR], 0.76; 95% CI, 0.73-0.79). Increasing patient age was associated with a higher diagnostic yield (OR, 1.02 per year; 95% CI, 1.01-1.03). Physician years of experience (OR, 1.01; 95% CI, 0.99-1.02; P = .39), physician sex (OR, 1.14; 95% CI, 0.79-1.63; P = .49), and studies originating from the emergency department (ER) (OR, 1.11; 95% CI, 0.75-1.65; P = .60) did not show a statistically significant association. When restricting the analysis to those studies performed by ER physicians, 123 of 974 (12.6%) were positive, and the OR for positivity for each additional 10 scans ordered decreased in a similar manner (OR, 0.74; 95% CI, 0.71-0.78).
Table. Positive CTPA Examinations for All Physiciansa.
| Study Volume | Physicians, No. | CTPA Studies, No. | Positive CTPA, No. (%) | ER Physicians, No. (%) | Other Physicians, No. (%) |
|---|---|---|---|---|---|
| 1-10 | 145 | 411 | 85 (20.7) | 13 (9.0) | 132 (91.0) |
| 11-20 | 14 | 228 | 37 (16.2) | 8 (57.1) | 6 (42.9) |
| 21-30 | 9 | 198 | 30 (15.2) | 8 (88.9) | 1 (11.1) |
| 31-40 | 6 | 179 | 20 (11.2) | 5 (83.3) | 1 (16.7) |
| 41-50 | 5 | 219 | 19 (8.7) | 5 (100) | 0 |
| >50 | 3 | 159 | 8 (5.0) | 3 (100) | 0 |
| Total | 182 | 1394 | 199 (14.2) | 42 (23.1) | 140 (76.9) |
Abbreviations: CTPA, CT pulmonary angiogram; ER, emergency department; NA, not applicable.
Physicians were stratified by the total study volume they ordered during the observation period.
Discussion
Our institutional yield of positive CTPA was 14.3%, which is similar to prior reported studies. However, closer inspection demonstrated that there was substantial interphysician variability, with individual positivity rates ranging between 0% to 33.3%. Our study suggests that individual demographic features, such as specialty and professional experience are not significantly associated with diagnostic yield; however, physicians who ordered a greater volume of scans compared with their peers had a markedly reduced diagnostic yield.
Limitations
Limitations of our study included its retrospective design and the inadequate charting of parameters, which precluded the derivation of a preexamination clinical probability score. In addition, owing to limitations in data collection, we were unable to determine the denominator of patients presenting with PE-related symptoms examined by each physician. Notably, in the cohort of ER physicians shift allotment was generally randomized and we did not observe any systematic biases.
Conclusions
Among physicians who ordered a greater number of CTPA scans, we observed a statistically significant decrease in the proportion of positive results. This association may reflect a fundamental relationship between individual physician overutilization and decreasing diagnostic yield, and is deserving of greater attention. Peer-relative rates of utilization are easily quantified from electronic databases, and can identify physicians most likely to benefit from individual performance feedback and decision support tools. Based on these findings, our group has designed automated yield monitoring and feedback, with the aim of closing the gap between individual physician performance in our institution. We hope this will translate to a substantial reduction in unnecessary CTPA scans along with the associated complications that may occur owing to unnecessary radiation, overdiagnosis, and overtreatment.
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