title: Relative-risk ratio was a useful measure of differential association in cohort and case-series studies.
abstract: OBJECTIVE
  The framework consists of cohort or case-series studies with intermittent exposure and two types of events. The aim is to define and estimate an association measure between the exposure and the occurrence of one type of event rather than the other.
  
  
  METHODS
  The model and the estimation method are obtained by extending Farrington's approach for one type of recurrent event. The proposed association measure "RR(c)" is the ratio of the relative risks pertaining to each type of event. The estimated RR(c) and its confidence interval are derived under the independence assumption between the counts of the two types of events. The data that are analyzed are part of the data of a study on antimicrobial resistance in children.
  
  
  RESULTS
  An interpretation of the RR(c) is proposed in terms of an odds ratio, which parallels a similar association measure defined in cross-sectional studies ("OR(c)"). The estimated value of the RR(c) agrees with the OR(c) reported in previous studies.
  
  
  CONCLUSIONS
  The RR(c) appears as a useful tool for evaluating the risk of colonization (or infection) with resistant rather than susceptible bacteria following a previous intake of a given antibiotic conditional on colonization (or infection) with any bacteria.
authors.affiliation: INSERM U780, Villejuif F-94807; Univ Paris-Sud, France. hocine@vjf.inserm.fr
authors.forename: M N
authors.initials: MN
authors.lastname: Hocine
authors.forename: P
authors.initials: P
authors.lastname: Tubert-Bitter
authors.forename: T
authors.initials: T
authors.lastname: Moreau
authors.forename: M
authors.initials: M
authors.lastname: Chavance
authors.forename: E
authors.initials: E
authors.lastname: Varon
authors.forename: D
authors.initials: D
authors.lastname: Guillemot
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D016001:Confidence Intervals; D003627:Data Interpretation, Statistical; D024881:Drug Resistance, Bacterial; D006801:Humans; D016017:Odds Ratio; D009960:Oropharynx / Q000382:microbiology; D010400:Penicillin G / Q000494:pharmacology; D018570:Risk Assessment / Q000379:methods*; D013296:Streptococcus pneumoniae / Q000187:drug effects
chemical_list: D000900:Anti-Bacterial Agents; D010400:Penicillin G