Definitions and outcomes of nutritional interventions in children with respiratory infections: the approach of the COMMENT initiative.

BACKGROUND/AIMS: This study is aimed at assessing definitions and outcomes used to measure the effects of nutrition in the prevention and treatment of respiratory tract infections in childhood. METHODS: We reviewed clinical trials studying the impact of nutritional interventions on upper and lower respiratory tract infections (URTI and LRTI), focusing on definitions and key outcomes. RESULTS: Fifty trials were included (46 on prevention and 4 on treatment). The definitions of respiratory infections were highly heterogeneous. In 15 of the trials, URTI or LRTI were diagnosed by a pediatrician. In 30 trials, definitions were based on symptoms reported by family members or field-workers only. Five trials did not provide any specific definition. Incidence was the most common outcome measure reported in the trials on prevention, and duration and illness severity were the most common in the treatment trials. CONCLUSIONS: The results showed a major heterogeneity with the use of a wide array of different definitions and clinical end points. To overcome these limitations, outcome measures might be differentiated into two categories: 'direct outcomes' in which respiratory infections are diagnosed and monitored by physicians according to rigorous definitions and 'indirect outcomes' (e.g. chest X-ray, antibiotic prescription and hospitalizations) to assess the burden of respiratory illnesses. Agreement on standard definitions and end points is needed to drive future trials.