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Chronic sequelae of E. coli O157: systematic review and meta-analysis of the proportion of E. coli O157 cases that develop chronic sequelae.

OBJECTIVE
This was a systematic review and meta-analysis to determine the proportion of Escherichia coli O157 cases that develop chronic sequelae.


DATA SOURCES
We conducted a systematic review of articles published prior to July 2011 in Pubmed, Agricola, CabDirect, or Food Safety and Technology Abstracts.


STUDY SELECTION
Studies were selected that reported the number of E. coli O157 cases that developed reactive arthritis (ReA), hemolytic uremic syndrome (HUS), irritable bowel syndrome, inflammatory bowel disease, or Guillain Barré syndrome.


METHODS
Three levels of screening and data extraction of articles were conducted using predefined data fields. Meta-analysis was performed on unique outcome measures using a random-effects model, and heterogeneity was assessed using the I² value. Meta-regression was used to explore the influence of nine study-level variables on heterogeneity.


RESULTS
A total of 82 studies were identified reporting 141 different outcome measures; 81 reported on HUS and one reported on ReA. Depending on the number of cases of E. coli O157, the estimate for the proportion of E. coli O157 cases that develop HUS ranged from 17.2% in extra-small studies (<50 cases) to 4.2% in extra-large studies (>1000 cases). Heterogeneity was significantly associated with group size (p<0.0001); however, the majority of the heterogeneity was unexplained.


CONCLUSIONS
High unexplained heterogeneity indicated that the study-level factors examined had a minimal influence on the variation of estimates reported.