Validation of a 7-point Global Overall Symptom scale to measure the severity of dyspepsia symptoms in clinical trials S. J. O. VELDHUYZEN VAN ZANTEN*, N. CHIBA   , à , D. ARMSTRONG à , A. N. BARKUN§, A. B. R. THOMSON – , V. MANN**, S. ESCOBEDO**, B. CHAKRABORTY** & K. NEVIN** *Divisions of Gastroenterology, Dalhousie University, Halifax, NS;  Divisions of Gastroenterology, Surrey GI Research, Guelph; àDivisions of Gastroenterology, McMaster Univer- sity, Hamilton, ON; §Divisions of Gastroenterology, McGill University, Montre ´al, QC; –Divisions of Gastroen- terology, University of Alberta, Edmonton; **Divisions of Gastroenter- ology, AstraZeneca Canada, Mississauga, ON, Canada Correspondence to: Dr S. J. O. Veldhuyzen van Zanten, Division of Gastroenterology, Queen Elizabeth II Health Sciences Centre, 1278 Tower Road, Room 928 Victoria Building, Halifax, NS B3H 2Y9, Canada. E-mail: zanten@dal.ca Publication data Submitted 22 August 2005 First decision 30 August 2005 Resubmitted 31 October 2005 Resubmitted 21 November 2005 Accepted 22 November 2005 SUMMARY Background Currently there is no consensus on the optimal method to measure the severity of dyspepsia symptoms in clinical trials. Aim To validate the 7-point Global Overall Symptom scale. Methods The Global Overall Symptom scale uses a 7-point Likert scale ranging from 1 ¼ no problem to 7 ¼ a very severe problem. Validation was per- formed in two randomized-controlled trials (n ¼ 1121 and 512). Con- struct validity: Global Overall Symptom was compared with the Quality of Life in Reflux And Dyspepsia, Gastrointestinal Symptom Rating Scale, Reflux Disease Questionnaire and 10 specific symptoms using Spearman correlation coefficients. Test–retest reliability: The Intraclass Correlation Coefficient was calculated for patients with stable dyspepsia defined by no change in Overall Treatment Effect score over two visits. Responsive- ness: effect size and standardized response mean were also calculated. Results Construct validity: Change in Global Overall Symptom score correlated significantly with Quality of Life for Reflux And Dyspepsia, Gastrointes- tinal Symptom Rating Scale, Reflux Disease Questionnaire and specific symptoms (all P < 0.0002). Reliability: The Intraclass Correlation Coeffi- cient was 0.62 (n ¼ 205) and 0.42 (n ¼ 270). Responsiveness: There was a positive correlation between change in Global Overall Symptom and change in symptom severity. The effect size and standardized response mean were 1.1 and 2.1, respectively. Conclusion The Global Overall Symptom scale is a simple, valid outcome measure for dyspepsia treatment trials. Aliment Pharmacol Ther 23, 521–529 Alimentary Pharmacology & Therapeutics ª 2006 The Authors 521 Journal compilation ª 2006 Blackwell Publishing Ltd doi:10.1111/j.1365-2036.2006.02774.x