Differences in the Occurrence and Cause of Medically-Attended Acute Gastroenteritis among Men who Have Sex with Men within an Integrated Health Care Delivery System

Background:  Men who have sex with men (MSM) are known to be at greater risk for outbreaks of acute gastroenteritis (AGE) due to certain pathogens, such as Shigella and Entamoeba. The goal of this work was to better characterize the occurrence of, and laboratory-confirmed pathogens associated with, medically-attended acute gastroenteritis (MAAGE) cases among MSM seen during the first 12 months of an active surveillance project within Kaiser Permanente Northwest (KPNW).

Methods:  We included male KPNW members, 18 years and older, enrolled continuously from 4/1/2014-3/31/2015 and with at least one health care encounter since 1/1/2010. We identified MAAGE encounters based on ICD-9 and chief complaint codes recorded in the electronic health record (EHR) during the surveillance period. We abstracted sex partner information and clinical laboratory testing results from the EHR and obtained enteric viral laboratory results from a surveillance-specific dataset.

Results:  Of our total population, 42,612 participants (27%) had a sex partner recorded. The incidence of MAAGE among MSM (2,085 episodes per 10,000) was 2.6 times that among non-MSM (794 per 10,000), and the proportion of individuals with at least one MAAGE encounter (7.7%) was 2.4 times higher than that among non-MSM (3.2%, p<0.0001). Among those with no sex partner reported, 6.6% had at least one MAAGE encounter and MAAGE incidence was 657 per 10,000. While clinical testing for enteric pathogens did not differ overall, a higher proportion of MSM had ova & parasite testing (46%) than did non-MSM (18%; p<0.0001). Among those tested for respective pathogens, MSM have a significantly higher proportion due to Shigella (4% vs 0%, p=0.016). Higher proportions of MAAGE due to Entamoeba (3% vs. 1%), astrovirus (6% vs. 1%), and rotavirus (6% vs. 1%) – and a lower one due to norovirus (6% vs. 13%) – trended to, but did not reach statistical significance.

Conclusion: Our findings suggest a higher incidence of MAAGE, as well as a difference in clinical testing procedures and pathogens associated with MAAGE, among MSM compared to non-MSM. Increased capture of sexual history information within the EHR, continued surveillance, and further research on the burden and causes of MAAGE in this population are warranted.