Regional Variation of Infectious Agents Causing Inpatient Endogenous Endophthalmitis in the US: A National Analysis

Abstract

To describe regional variation in microbes causing infectious endogenous endophthalmitis (EE) in the US. This is a retrospective, national database analysis utilizing the 2002-2014 National Inpatient Sample (NIS) database. Using the International Classification of Disease 9 (ICD-9) codes, we identified cases with EE. Cases were stratified regionally into Northeast, South, West, or Midwest. Unadjusted chi-square analysis followed by adjusted multivariate logistic regression was performed to evaluate variation in demographic factors, comorbidities using the Elixhauser Comorbidity Index (ECI), microbial variation, mortality, and use of vitrectomy or enucleation by region. Proportion of microbes, mortality, and vitrectomy by region in addition to factors with significant odds ratios for mortality and for in-hospital vitrectomy. A total of 10,912 patients with infectious EE were identified, with 2,063 cases in the Northeast (18.9%), 2,145 cases in the Midwest (19.7%), 4,134 cases in the South (37.9%), and 2,570 cases in the West (23.6%). Chi-square analysis indicated significant regional variation in patient demographics, microbes causing the infection, Elixhauser Comorbidity Index, mortality, and surgical intervention. The four most common microbes for all regions were methicillin-sensitive Staphylococcus aureus (MSSA), Streptococcus, Candida, and methicillin-resistant Staphylococcus aureus. MSSA was the most common cause of EE in all regions, though the proportion of MSSA infection did not significantly vary by region (p=0.027). Further, there was significant regional variation in the proportion of other microbes causing the infection (p<0.001). Higher rates of vitrectomies were seen in the South and Midwest regions compared to the Northeast and West (p=0.041). Regional variation exists in the infectious microbes causing EE. Further studies are needed to elucidate the etiology of these variations.