Validation of a 7-point Global Overall Symptom scale to measure the severity of dyspepsia symptoms in clinical trials.
BACKGROUND
Currently there is no consensus on the optimal method to measure the severity of dyspepsia symptoms in clinical trials.


OBJECTIVE
To validate the 7-point Global Overall Symptom scale.


METHODS
The Global Overall Symptom scale uses a 7-point Likert scale ranging from 1 = no problem to 7 = a very severe problem. Validation was performed in two randomized-controlled trials (n = 1121 and 512). Construct 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. Responsiveness: 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, Gastrointestinal Symptom Rating Scale, Reflux Disease Questionnaire and specific symptoms (all P < 0.0002). Reliability: The Intraclass Correlation Coefficient was 0.62 (n = 205) and 0.42 (n = 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.


CONCLUSIONS
The Global Overall Symptom scale is a simple, valid outcome measure for dyspepsia treatment trials.
Veldhuyzen van Zanten
S J O
SJ
Division of Gastroenterology, Dalhousie University, Halifax, NS, Canada. zanten@dal.ca
Chiba
N
N
Armstrong
D
D
Barkun
A N
AN
Thomson
A B R
AB
Mann
V
V
Escobedo
S
S
Chakraborty
B
B
Nevin
K
K
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000897:Anti-Ulcer Agents / Q000627:therapeutic use; D004415:Dyspepsia / Q000150:complications / Q000175:diagnosis* / Q000188:drug therapy; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009853:Omeprazole / Q000627:therapeutic use; D011788:Quality of Life; D016032:Randomized Controlled Trials as Topic; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires; D016896:Treatment Outcome
D000897:Anti-Ulcer Agents; D009853:Omeprazole