S. Dell-Kuster, Raoul Droeser, J. Schaefer, V. Gloy, H. Ewald, S. Schandelmaier, L.G. Hemkens, H.C. Bucher, J. Young,
Status: completed Duration: Feb 2013 - Jan 2018
Multiple surgical procedures in a single patient are relatively common and lead to dependent (clustered) data. This dependency needs to be accounted for in study design and data analysis. A systematic review between 2004 and 2013 was performed to assess how clustered data were handled in RCTs including patients undergoing unilateral or bilateral inguinal hernia repair. Study characteristics determining the appropriateness of handling clustered data were extracted. Using simulations, various statistical methods accounting for clustered data were compared with an analysis ignoring clustering.\nClustering was rarely considered in inguinal hernia trials. The simulations underline the importance of considering clustering as part of the statistical analysis to avoid false-positive and false-negative results, and hence inappropriate study conclusions.