Estimates of intraclass correlation coefficient and design effect for surveys and cluster randomized trials on injection use in Pakistan and developing countries

Abstract

To assess injection practices and to test interventions aimed at reducing unsafe injections in developing countries, cluster surveys and cluster randomized trials are needed. The design of cluster-based studies requires estimates of intraclass correlation coefficients that have to be obtained from previous studies. This study presents such estimates. Data were derived from a cross-sectional study of injection use and health seeking in Pakistan that used 34 clusters to select 1150 study subjects aged > or =3 months. We analysed variance to separate its components. Most of intraclass correlation coefficients were in the range of 0.01-0.05. For proportion of injections received during last 3 months, mean number of injections received and health seeking during the past 3 months the intraclass correlation coefficients were 0.02, 0.04 and 0.02, respectively. These estimates can be useful in designing cluster surveys and cluster randomized trials for injection safety in Pakistan and other developing countries.