Reproducibility, validity, and responsiveness of a disease-specific symptom questionnaire for gastroesophageal reflux disease

The purpose of this study was to establish the reproducibility, validity, a nd responsiveness of a symptom questionnaire to assess patients with gastro esophageal reflux disease (GERD). A total of 300 patients with GERD complet ed questionnaires before and 6 months after laparoscopic Nissen fundoplicat ion. Forty-six GERD patients who continued on omeprazole served as controls . Lower esophageal sphincter pressure, 24-h pH, and quality of life (SF36) were measured at baseline and follow-up. Reproducibility was calculated as an intraclass correlation coefficient (ICC) from a repeated-measures analys is of variance on symptom scores (SS) on two consecutive days. Validity was established by correlating SS with 24-h pH and SF36 scores. Responsiveness was calculated as the the ratio of the mean paired difference in score in the surgical group to the within-subject variability in control subjects. R eproducibility was very high, as revealed by an ICC of 0.92. Strong correla tions between SS and SF36 scores at baseline and after surgery demonstrated high cross-sectional validity. Correlation between change in SS and change in pH, SF36 pain, general health, and physical health scores demonstrated longitudinal validity. The mean (95% confidence interval) paired difference s in SS were 25.6 (23.7, 27.5) in the study and 2.0 (-3.2, 7.3) in the cont rol groups, and the responsive index was 1.0. The estimated minimally impor tant clinical difference was 7. We conclude that the symptom score is a rep roducible, valid, and responsive instrument for assessing symptoms caused b y GERD.