INTRACLUSTER CORRELATIONS OF STI AND SEXUAL BEHAVIOUR OUTCOMES: ESTIMATES FROM A COMMUNITY-BASED CLUSTER RCT

Abstract

Interventions to prevent or manage sexually transmitted infections (STI) are often evaluated at the clinic or community level. Cluster randomised controlled trials (cluster-RCT) need to take into account similarities between characteristics within clusters, increasing the required sample size. However, information about intracluster correlation coefficients (ICC) is rarely known at the design stage. We estimated ICCs for four STI and sexual behaviour variables at the levels of clinic and postcode. Data were collected during the Australian Chlamydia Control Effectiveness Pilot (ACCEPt), a cluster-RCT of a chlamydia testing intervention in women and men aged 16–29 years attending general pract..