Objective: Standardized outcome measures provide a basis for comparing outcomes of different clinical trials. Consequently, they can serve as the foundation for determining which therapeutic interventions are most effective. The aim of the present study is to systematically assess how definitions and outcome measures are defined in therapeutic randomized controlled trials (RCTs) of children with functional constipation (FC).
Methods: PubMed, EMBASE, and Cochrane databases were searched. Studies were included if it was a (systematic review of) therapeutic RCT, concerning children from 1 to 18 years old with FC, a definition of FC was provided, and if they were written in English. The Delphi list was used for quality assessment.
Results: A total of 4092 articles were found but only 45 studies fulfilled our inclusion criteria. In these 45 trials, 22 different definitions of FC were used (17 studies used the Rome III-criteria), 27 different interventions were investigated, and 29 different definitions of treatment success were used. Thirty RCTs (57%) reported primary outcomes of which treatment success was the most frequently used. Most trials (80%) used parental diaries of which only 2 RCTs stated that their instrument was validated. Twenty-four trials (53%) were of good methodological quality.
Conclusions: Inconsistency and heterogeneity exist in definitions and outcome measures used in RCTs on childhood FC. Standard definitions, outcome measures, and also validated instruments are needed. We recommend the development of a minimum core outcome set for clinical research in children with FC to make comparison possible between the effects of different therapeutic interventions across studies.