Psychometric evaluation of patient-reported outcomes in irritable bowel syndrome randomized controlled trials: a Rome Foundation report.
OBJECTIVE
There is debate about how best to measure patient-reported outcomes (PROs) in irritable bowel syndrome (IBS). We pooled data to measure the psychometric properties of IBS end points, including binary responses (eg, "adequate relief") and 50% improvement in symptom severity.


METHODS
We pooled data from 12 IBS drug trials involving 10,066 participants. We tested the properties of binary response and 50% improvement end points, including the impact of baseline severity on performance, and measured construct validity using clinical anchors.


RESULTS
There were 9044 evaluable subjects (age, 44 years; 85% female; 58% IBS constipation-prominent [IBS-C]; 31% IBS diarrhea-prominent [IBS-D]). Using the binary end point, the proportion responding in the mild, moderate, and severe groups was 42%, 40%, and 38%, respectively (P = .0008). There was no effect of baseline severity on binary response (odds ratio [OR], 0.99; 95% confidence interval [CI], 0.99-1.0; P = .07). The proportions reaching 50% improvement in pain were 45%, 41%, and 41%, respectively; there was a small, yet significant, impact of baseline severity (OR, 1.04; 95% CI, 1.03-1.05; P < .0001) that did not meet clinical relevance criteria. Both end points revealed strong construct validity and detected "minimally clinically important differences" in symptoms. Both provided better discriminant spread in IBS-D than IBS-C.


CONCLUSIONS
Both the traditional binary and 50% improvement end points are equivalent in their psychometric properties. Neither is impacted by baseline severity, and both demonstrate excellent construct validity. They are optimized for the IBS-D population but also appear valid in IBS-C.
Spiegel
Brennan
B
Department of Medicine, VA Greater Los Angeles Healthcare System, Los Angeles, California, USA. bspiegel@mednet.ulca.edu
Camilleri
Michael
M
Bolus
Roger
R
Andresen
Viola
V
Chey
William D
WD
Fehnel
Sheri
S
Mangel
Allen
A
Talley
Nicholas J
NJ
Whitehead
William E
WE
D015746:Abdominal Pain / Q000209:etiology / Q000517:prevention & control* / Q000523:psychology; D000328:Adult; D005260:Female; D006801:Humans; D043183:Irritable Bowel Syndrome / Q000150:complications / Q000175:diagnosis / Q000523:psychology / Q000628:therapy*; D016015:Logistic Models; D008297:Male; D016017:Odds Ratio; D010147:Pain Measurement; D017060:Patient Satisfaction; D011237:Predictive Value of Tests; D011594:Psychometrics; D016032:Randomized Controlled Trials as Topic; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D016896:Treatment Outcome
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