Discussion
Over the past decade, the diagnosis of PE has remained an important public health issue. Our findings here demonstrate that the number of patients seen in the ED who were given a diagnosis of PE more than doubled from 2001 to 2010. However, when adjusted for CT utilization, there was no significant rise over this time period in the likelihood of a diagnosis of PE among patients seen in the ED. Thus, the apparent rise in ED visits with a diagnosis of PE may be attributed in large part to the increased availability and use of CTPA, rather than reflecting a true rise in the incidence of PEs in the US. An aging population may have contributed to a true increase in PE diagnosis, but our data do not show a significant change in the proportion of patients with a diagnosis of PE 65 years and over during the study period. None of the other variables assessed changed significantly during the study period, including sex, race, geographic region, Metropolitan Statistical Area status, hemodynamic status, and admission to the hospital. Overall then, our data suggest that the use of CTPA has contributed to the substantial increase in PE diagnosis.
Our data further suggest that many patients given a diagnosis of PE in the ED may have been unnecessarily hospitalized. Most patients in EDs with a diagnosis of PE were hemodynamically stable at presentation, with stability defined using cutoff values from the pulmonary embolism severity index for prognostication in patients with acute symptomatic PE. Subsequent in-hospital mortality was under 3%, which agrees with the low mortality rates recently reported in in 22 community and academic EDs in the US. The vast majority of patients with a diagnosis of PE were nonetheless admitted to the hospital. Rates of admission for patients with a diagnosis of PE in the ED remained stable throughout the study period at approximately 86%, compared to approximately 15% for all other ED visits.
There is now good evidence that hemodynamically stable patients should be considered candidates for outpatient management. We observed, however, than only about 10% of ED PE patients were discharged from the ED for outpatient management. Recommended prerequisites for outpatient management include the absence of serious co-morbid conditions (e.g. significant heart disease, renal or liver failure) or recent bleeding, as well as adequate social support. Recently published data suggest that approximately 50% of patients with acute PE can be treated safely as outpatients. There is great potential for healthcare cost savings; the average cost of admission for PE in a recent analysis was over $8,000.
Over the study period, ED visits that included a diagnosis of PE comprised approximately 0.08% of all ED visits. Those diagnosed with PE in the ED were older than the population seen in the ED with diagnoses exclusive of PE, not surprising since older age is a known risk factor for PE. Nonetheless, most visits with a diagnosis of PE in the ED (approximately 56%) were under 65 years old, which agrees with data recently reported in a multicenter study assessing clinical characteristics of suspected or confirmed PEs in the ED. Our data further reinforces the need to consider PE among younger patients.
There were a number of limitations to our study. The retrospective design limits the data available for analysis. For example, the use of ICD-9 codes to identify visits for PE does not differentiate between suspected and confirmed PEs. Furthermore, we cannot assess how the PE was diagnosed and whether or not the PE was acute, chronic, or recurrent. While the use of ICD-9 codes has been validated in hospitalized patients, there is data to suggest that PE diagnostic codes reported in EDs should be used with caution. It is therefore possible that the true incidence of PE has not changed and that our observed increase is largely related providers more often including PE as a provisional diagnosis in the ED. We nonetheless feel this is an important finding – ED doctors may be more often considering the diagnosis of PE in the era of more readily available CTPA. It is also possible that patients with chronic or recurrent PEs are presenting to the ED with increased frequency. While it is likely that some PEs were not diagnosed in the ED, we do not believe this underestimation would have changed over time and therefore trend analysis should not have been significantly impacted. Since NHAMCS had a combined CT and MRI variable between 2001 and 2004, we cannot distinguish which of the two technologies were utilized. However, this is unlikely to pose a significant problem—there were no patient visits with a diagnosis of PE in the ED that underwent MRI alone between 2005 and 2010, and therefore it can be assumed that no or very few patients underwent MRI alone when the combined CT/MRI variable was reported positive between 2001 and 2004. NHAMCS does not include data on the utilization of ventilation/perfusion lung scans. Since mortality in patients diagnosed with PE was infrequent, we were unable to generate robust confidence intervals for these characteristics or assess for trends. We can, however, confidently conclude that in-hospital mortality in patients diagnosed with PE in the ED was very low and this agrees with recently reported data. Finally, it is possible that the changing demographics of the US population could account for the increase in proportion of ED visits with a diagnosis of PE.