Acute pulmonary embolism (PE) is a common disease with varying presentations, necessitating risk stratification to determine management. Measurement of right ventricle (RV) to left ventricle (LV) ratio >=1.0 on computed tomography pulmonary angiogram (CTPA) suggests RV strain, which may indicate a worse prognosis. Two prior studies showed that residents with brief training by a radiologist could accurately measure RV/LV ratio on CTPA. In this study, we assessed whether medical students could accurately measure RV dilatation on CTPA.
We conducted a post hoc analysis of a retrospective cohort study of adults undergoing management for acute PE at 21 community Emergency Departments across Kaiser Permanente Northern California (KPNC) from 2013 to 2015. We created a sample of 120 patients from the original 2,387 patients, stratified to contain an equal number of patients from each of the five Pulmonary Embolism Severity Index classes. The sample had a proportional ratio of home/short stay to hospitalized patients. Four medical students measured RV and LV diameter on CTPA after a series of brief training sessions from an emergency medicine physician and an interventional radiologist. We used Cohen’s kappa statistics, Bland-Altman plots, and Pearson correlation coefficients to assess interrater reliability, comparing the student measurements with those of the radiologist.
Of the 120 CTPAs, 108 images were accessible and constitute the study cohort. Among the 108 CTPAs, 79 (73%) showed RV dilatation and 29 (27%) did not. The kappa statistic for the presence of RV dilatation of the medical students compared to the radiologist showed moderate agreement for 3 medical students (kappa (95% CI): 0.46 (0.21-0.70), 0.49 (0.31-0.68), 0.50 (0.32- 0.68)) and fair agreement for one medical student (kappa (95% CI): 0.29 (0.10- 0.47)). The average interrater differences in RV/LV ratio between a radiologist and each of the four medical students were -0.04, -0.05, 0.04, and 0.24. Pearson correlation coefficients were 0.87, 0.80, 0.74, and 0.78, respectively, indicating moderate correlation (p<0.001 for all).
With brief training, medical students were able to identify RV dilatation on CTPA in moderate agreement with that of a radiologist. Further study is needed to determine whether medical student accuracy could improve with additional training.