Symptom overlap in patients with upper gastrointestinal complaints in the Canadian confirmatory acid suppression test (CAST) study: further psychometric validation of the reflux disease questionnaire

BACKGROUND: The reflux disease questionnaire (RDQ) is a short, patient-completed instrument. AIMS: To investigate the psychometric characteristics of the RDQ in patients with heartburn-predominant (HB) and non-heartburn predominant (NHB) dyspepsia. METHODS: HB (n = 388) and NHB (n = 733) patients were randomized to esomeprazole 40 mg daily or twice daily for 1 week, followed by 3 weeks of esomeprazole 40 mg daily. RESULTS: High factor loadings (0.78-0.86) supported the 'regurgitation' dimension of the RDQ. Overlapping factor loadings in the 'heartburn' and 'dyspepsia' dimensions suggested symptom overlap. All dimensions demonstrated high internal consistency (Cronbach's alpha: 0.79-0.90). Intra-class correlation coefficients over 4 weeks were good (0.66-0.85). The RDQ showed good responsiveness over 4 weeks of treatment, with high effect sizes (> or =0.80). Moderate or large symptom improvements were reported by 90% and 77% of HB and NHB patients, respectively, following treatment. Patients who responded to acid suppression also experienced symptom benefits in all RDQ dimensions. CONCLUSIONS: The RDQ is reliable, valid and responsive to change in HB and NHB patients. The symptom overlap is important but need not play a major role in determining treatment strategy as both patient groups benefited from proton pump inhibitor treatment.