Objective Core outcome sets are the baseline for what should be measured in clinical research and, thus, should serve as a guide for what should be collected and reported. The Consensus Group on Outcome Measures Made in Pediatric Enteral Nutrition Clinical Trials, established in 2012, agreed that consensus on a core set of outcomes with agreed-upon definitions that should be measured and reported in clinical trials was needed. To achieve this goal, six working groups (WGs) were setup, including WG on acute diarrhoea, whose main goal was to develop a core outcome set for trials in acute diarrhoea.

Methods The first step identified how published outcomes related to acute diarrhoea were reported. The second focused on the methodology for determining which outcomes to measure in clinical trials. The third employed a two-phase questionnaire study using the Delphi technique to define clinically important outcomes to clinicians and parents.

Results For therapeutic studies, the five most important outcome measures were diarrhoea duration, degree of dehydration, need for hospitalisation (or duration of hospitalisation for inpatients), the proportion of patients recovered by 48 h and adverse effects. The prophylactic core outcome set included prevention of diarrhoea, prevention of dehydration, prevention of hospitalisation and adverse effects.

Conclusions The outcome sets for therapy and prevention can be recommended for use in future trials of patients with gastroenteritis. Their envisioned goal is to decrease study heterogeneity and to ease the comparability of studies. WG's next step is to determine how to measure the outcomes included in the core set.