Measuring Symptom Distress and Health-Related Quality of Life in Clinical Trials of Gastroesophageal Reflux Disease Treatment: Further Validation of the Gastroesophageal Reflux Disease Symptom Assessment Scale (GSAS)
This study reports the reliability and validity of the distress subscale of the GERD Symptom Assessment Scale (GSAS) and the acute SF-36 Health Survey in a clinical trial setting. Patients with moderately severe GERD completed the GSAS and SF-36 at baseline and four weeks following treatment. The age (mean ± sd) of the 187 patients was 45.5 ± 11.1 years and most were female (63%) and Caucasian (78%). All scales met the 0.70 reliability criterion except for the SF-36 bodily pain scale. Mean baseline GSAS scores were significantly (P < 0.001) poorer by 10–17% among patients reporting more severe levels of all symptoms. Mean baseline SF-36 physical component summary scores were significantly (P < 0.02) poorer among patients reporting more severe levels of regurgitation, early satiety, bloating, and nausea. Patients reporting complete and satisfactory heartburn relief reported improvements in GSAS scores that were 13% and 10% greater, respectively, than patients who did not experience these levels of relief (P < 0.001). In conclusion, the GSAS and SF-36 scales were reliable and valid measures in this clinical trial. Differences of 10% in GSAS distress scores correspond to differences in symptom severity at a point in time and to changes in symptom severity over time. The SF-36 was not as useful in detecting differences in symptom severity over time.