Statistical methods in the Global Enteric Multicenter Study (GEMS).

The Global Enteric Multicenter Study (GEMS) is an investigation of the burden (number of cases and incidence) of moderate-to-severe diarrhea (MSD) in children <60 months of age at 7 sites in sub-Saharan Africa and South Asia. The population attributable fraction for a putative pathogen, either unadjusted or adjusted for other pathogens, is estimated using the proportion of MSD cases from whom the pathogen was isolated and the odds ratio for MSD and the pathogen from conditional logistic regression modeling. The adjusted attributable fraction, proportion of MSD cases taken to a sentinel health center (SHC), number of cases presenting to an SHC, and the site's population are used to estimate the annual number of MSD cases and MSD incidence rate attributable to a pathogen or group of pathogens. Associations with death and nutritional outcomes, ascertained at follow-up visits to case and control households, are evaluated both in MSD cases and in the population.