Table 4 IRIS: training program to increase identification of female victims of domestic violence
From: Heterogeneity in pragmatic randomised trials: sources and management
Participants: Women aged over age 16 Centres: General practices Intervention: Practice-based training sessions and pop-up template in electronic medical record Control: Usual care Outcome: Number of referrals Design: Two parallel-group, cluster randomised trial, clusters being general practices | |
Centre selection | “To ensure inclusion of practices with a range of characteristics, we stratified them by four characteristics (proportion of whole time equivalent female doctors, general practice postgraduate training status, number of patients registered with the practice, and percentage of the practice population on low incomes defined by the low income scheme index), then ordered them randomly within strata and invited them to participate in the trial sequentially within each strata by email or letter.” |
Variability in cluster (centre) size | “With 24 intervention practices and 24 control practices, with the assumption of an identification rate of 1% in control practices (a conservative estimate based on our survey of 12 east London practices) and an intracluster correlation coefficient of 0·03, we would be able to detect a difference of 5·2% in the identification rate with a power of 80% at a significance level of 0·05. This calculation assumed an average of 1600 women in the relevant age group in every practice, and took account of variation in cluster size.” |
Randomisation | “To ensure inclusion of practices with a range of characteristics, we stratified them by four characteristics (…).” “Within every primary care trust area we randomised practices with a computer minimisation programme, with a random component (Minim Version 1.3), maintaining allocation concealment. JR ran the minimisation programme for every practice after they were recruited and then informed the research associates of the allocation. The minimisation variables were the same as the stratification variables.” |
Statistical analysis | “Analysis was done for all practices for which we obtained baseline data, adjusted for minimisation factors (…).” |