Table 1

Selected characteristics of the seven eligible articles

CharacteristicDelaney et al. (34)Dial et al. (17)Hirschhorn et al. (19)Kuntz et al. (9)Levy et al. (20)Naggie et al. (36)Wilcox et al. (27)
Publication yr2007200819942011200020112008
Study designCase controlNested case controlRetrospective cohortNested case controlNested case controlCase controlCase control
Data source(s)UK General Practice Research Database (GPRD) and British National FormularyHospital discharge summary and medical insurance records of Quebec, CanadaHarvard Community Health PlanUniversity of Iowa Wellmark Data Repository (Iowa and South Dakota, USA)United Health Group claims databaseDuke University Medical Center, Durham Regional Hospital, Durham, Salisbury, and Asheville VAMCsaUK laboratory test results and telephone questionnaire
Study periodbJan. 1993 to Dec. 2004Jan. 1996 to Dec. 2004Apr. 1988 to Nov. 1990Jan. 2004 to Dec. 2007Jan. 1992 to Dec. 1994Oct. 2006 to Nov. 2007Jan. to Dec. 1999
Study populationPersons registered in GPRD not hospitalized in the last yrPersons ≥ 65 yrs old, with at least one previous hospitalization, without hospital discharge in the previous 90 daysEnrollees not hospitalized in the last 42 days and with ≥1 antibiotic prescription in the previous 2 to 42 daysEnrollees with >12 mo of health coverage without discharge in the previous 12 wksEnrollees with a C. difficile lab test and with exactly 1 antibiotic exposure in the previous 2 to 42 daysOutpatients ≥ 18 yrs old without history of diarrhea and without discharge in the previous 12 wksOutpatients with a fecal sample sent for C. difficile toxin test
Case definitionPresence of an initial positive C. difficile toxin assay result and/or a clinical diagnosis recorded by their general practitioner (GP)Primary hospital diagnosis of CDI (ICD coding)Positive assay result for C. difficile toxin with documented diarrhea or colitis with onset within 48 h of admissionPrimary or secondary CDI diagnosis on insurance claim. For hospital patients, it must be recorded at admission.Documented diarrhea and a positive C. difficile laboratory test result in the medical recordPatients with diarrhea (onset in community or ≤72 h of hospital arrival) and a positive stool toxin assay resultPatients presenting to their GP with symptoms of diarrhea with positive stool toxin assay result
MatchingAge, clinic site, and index datecIndex datec and date of 1st hospitalizationNoneIndex datecNoneIndex moc and clinic siteAge, sex, and index periodc (3 mo)
Antibiotic exposureNational claims database; 90-day windowProvincial claims database; 45-day windowHealth maintenance organization (HMO) pharmacy records; 2- to 42-day windowOutpatient drug claims; 180-day windowHMO pharmacy records; 2- to 42-day windowElectronic medical records; 90-day windowPostal questionnaire; 4-wk window
Adjustment methodConditional logistic regressionConditional logistic regressionStratificationConditional logistic regressionStratificationLogistic regressionMatching
No. of cases (n)/no. of controls (N)1,233/12,330836/8,36051/175,275d304/3,04048/358,389d66/11440/112
  • a VAMC, Veterans Affairs Medical Center.

  • b Jan., January; Dec., December; Apr., April; Nov., November; Oct., October.

  • c The index date (or month) was defined as the date of diagnosis, symptom onset, or admission for cases and the date of health care facility visit for controls.

  • d N = person-days.