Calendar month variation in the diagnosis and severity of pulmonary embolism

Background Pulmonary embolism (PE) is the third-leading cause of cardiovascular death in the United States, and several studies suggest PE shows seasonal variation. Variation in monthly PE diagnosis may be due to pathophysiologic factors or confounding/bias. However, severe PE may be less prone to diagnostic bias. To address this gap, we analyzed two registries from 1/2013–12/2018 with the aim of describing temporal trends in PE diagnosis and severity. Methods We performed a retrospective analysis of two existing databases containing: (1) consecutive patients diagnosed with PE in the emergency departments (EDs) of two large, urban teaching hospitals, and (2) severe PEs requiring PE Response Team (PERT) activation at one of the above hospitals. The primary outcome was to assess variation in PE diagnosis and severity by calendar month. Separate analysis of these two databases sought to control for workup bias by trainee experience across the academic year. One-way ANOVA and Poisson regression were performed to assess for cyclical variation across calendar months, using Stata v16.1. Results The PE diagnosis database contained 1324 patients over 36 months. One-way ANOVA did not reveal a statistically significant ( p = 0.713) association between calendar month and PE number. The PERT activation database contained 1082 patients over 72 months. One-way ANOVA revealed a statistically significant ( p = 0.024) association between calendar month and activations, repeated year-on-year. Conclusion Our results indicate correlation between calendar month and PERT activation; however, this pattern was not observed for PE diagnoses. This finding warrants further investigation into the causes of calendar month variation of PERT activations.