The clinical utility of the park nicollet digestive health status instrument for patients with gastroesophageal reflux disease

Abstract

PURPOSE: Effective clinical and research outcome instmments for GERD need to accurately measure the symptom complex (validity), provide consistent results when administered under similar conditions at two separate intervals (reliability), and reflect important clinical change over time or after a treatment intervention (responsiveness). The purpose of this study was to assess the usefulness of the Park Nicollet Digestive Health Status Instrument (DSHI) for clinical trials and clinical practice. The assessment focused on the criterion validity, test-retest reliability, and responsiveness of the GERDspecific subscale of the DHSI for patients with documented GERD. METHODS: Randomized controlled trial of 45 subjects meeting diagnostic criteria for GERD based on 24 hour ambulatory pH monitoring. All subjects filled out the DHSI along with a global assessment of health status at three time points: baseline, one week, and at four weeks. At the one week followup, subjects were randomized to receive either one month treatment with omeprazole 20 mg qd or placebo. Criterion validity was assessed by correlating scores on the GERD-specific domain with the 24-hour ambulatory pH test, a gold standard for GERD diagnosis using Pearson productmoment correlations. Test-retest reliability was assessed by comparing scores at entry and one week later using interclass correlation. Responsiveness was assessed by Student's t test for paired samples to evaluate changes in GERDspecific DHSI scores over time in patients who reported at least moderate improvement in their condition over time to those who remained clinically stable based on their own global assessments. RESULTS: Criterion validity analyses demonstrated significant convergence between GERD subscale scores and overall pH test results (r=.37, p=.02) and test-retest reliability as measured by the intraclass correlation coefficient was high (9=.84). For GERD patients with at least moderate improvement over time based on their global ratings, GERD scores improved significantly while no differences in GERD scores were observed for clinically stable patients (t=--5.92, p < .0001) thus indicating good responsiveness. CONCLUSION: The DHSI was designed both as a tool that would be useful to measure differences between people (discriminative instrument) and examine change over time (evaluative instrument). The present study represents the first rigorous test of the DHSI as a study outcome measure. The results demonstrate the DHSI can be used to monitor the status of patients with GERD over time. Future research will focus on similar investigations of patients with irritable bowel syndrome, peptic ulcer disease, and functional dyspepsia. Supported in part with an unrestricted grant from Astra-Merck, Inc.