Validation of a Parent Report Questionnaire: The Infant Gastrointestinal Symptom Questionnaire.

Objective. To evaluate the reliability and validity of the Infant Gastrointestinal Symptom Questionnaire (IGSQ), a tool to assess feeding tolerance in infants. Methods. Qualitative methods were used to develop IGSQ content across 5 symptom clusters, yielding a 13-item index of parent-reported infant digestion and elimination behaviors over the prior 7 days. Classical psychometric methods evaluated factor structure, interrater and retest reliability, and validity in 4 prospective studies of 836 infants. Results. Interrater and retest reliability were acceptable to good. IGSQ Index score was highly correlated (r = 0.89) with daily parent reports. IGSQ scores were significantly different between infants whose parents planned to switch formulas because of perceived feeding problems and those without parental concerns. Conclusions. The IGSQ is a practical, reliable, and valid method for assessment of infant gastrointestinal-related behaviors. Its use in clinical studies can provide empirical evidence to advance parent education regarding both normal and clinically meaningful feeding-related behaviors.