Validation of the Reflux Disease Questionnaire addressing to Greek patients with upper gastrointestinal symptoms in primary health care

Primary care physicians face challenges in diagnosing and managing Gastro-oesophageal reflux disease (GERD). The Reflux Disease Questionnaire (RDQ) meets the standards of validity, reliability, and practicability. This paper reports on the validation of the translated into Greek RDQ. RDQ is a condition specific instrument. For the validation of the questionnaire, the internal consistency of its items was established using the alpha coefficient of Chronbach, the reproducibility (test – retest reliability) was measured by kappa correlation coefficient and the criterion of validity was calculated against the diagnosis of another questionnaire already translated and validated into Greek (IDGP) using kappa correlation coefficient. A factor analysis was also performed. Greek RDQ showed a high overall internal consistency (alpha value: 0.91) for individual comparison. All 8 items regarding heartburn and regurgitation (GERD) had “good” reproducibility (Cohen's κ = 0.60 to 0.79), while the remaining 4 items about dyspepsia had a “moderate” reproducibility (Cohen's κ= 0.40 to 0.59). The kappa coefficient for criterion validity for GERD was rather poor (0.20, 95% CI: 0.04, 0.36) and the overall agreement between the results of the RDQ questionnaire and those based on the IDGP questionnaire was 70.5%. Factor analysis indicated three factors with Eigenvalue over 1.0, and responsible for 76.91% of variance. Regurgitation items correlated more strongly with the 3rd component but pain behind sternum and upper stomach pain correlated with the 2nd component. The Greek version of RDQ seems to be a reliable, valid and responsive instrument following the pattern of the original questionnaire, and could be used in primary care research in Greece