RESUMEN
BACKGROUND: Current questionnaires for assessing gastro-oesophageal reflux disease (GERD) symptoms are limited in their ability to capture nocturnal symptoms. AIM: To develop and validate an instrument, the Nocturnal Gastro-oesophageal Reflux Disease Symptom Severity and Impact Questionnaire (N-GSSIQ), to assess severity and impact of nocturnal GERD symptoms. METHODS: Two focus groups and 16 cognitive debriefing interviews were conducted among GERD patients to identify key issues about nocturnal symptoms. A draft instrument was tested in 196 patients at 11 clinics in the US to evaluate psychometric properties. Exploratory factor and item response theory analyses were conducted to finalize items and subscales. Internal consistency reliability, reproducibility and construct validity were examined. RESULTS: Mean age was 45 (s.d. = 13.8) years; 76% were female and 68% were Caucasian. Patient-rated severity was mild-moderate for 69% of participants; 48% reported symptoms on two to three nights the past week. The final questionnaire includes 20 items and three subscales: Nocturnal GERD Symptoms, Morning Impact of Nocturnal GERD and Concern about Nocturnal GERD. The subscales demonstrated internal consistency reliability (Cronbach's alpha 0.84-0.94) and were significantly correlated with similar measures and disease severity (0.41-0.81; P < 0.0001). CONCLUSION: The results support the reliability and validity of the N-GSSIQ as a measure of severity, morning impact and concern about nocturnal GERD.