Analyzing the content of outcome measures in clinical trials on irritable bowel syndrome using the international classification of functioning, disability and health as a reference.
BACKGROUND
Patients with irritable bowel syndrome (IBS) report a significant impact of their symptoms on functional health. In outcome assessment of clinical studies on IBS, however, functional aspects other than gastrointestinal symptoms seem to be disregarded to a great extent.


OBJECTIVE
To analyze the content of outcome measures used in clinical IBS trials.


METHODS
A systematic review was performed in terms of a quantitative content analysis using the International Classification of Functioning, Disability and Health (ICF) as a coding scheme. Outcome measures were selected from all randomized controlled trials on IBS published in PubMed from the beginning to April 2002. From the outcome measures pre-specified text passages, so-called coding units, were extracted and linked to the ICF. A coding unit had to describe a single health aspect or an internal or external factor with an impact on health. If the outcome measure was a test the goal of the test was semantically implicated. Only second-level ICF categories contained in the outcome assessment of at least 10 % of the studies were considered. All steps of the review were performed by three independent raters.


RESULTS
99 studies were included. Single items were used as outcome measures in 88, clinical and paraclinical tests in 42 and questionnaires in 24 studies. Ninety percent of the coding units (n = 2271) could be linked to the ICF. ICF categories describing gastrointestinal symptoms were considered in the outcome assessment of 37 to 85 studies depending on the type of content compared to extra-gastrointestinal symptoms in 10 to 22 studies. Health information of ICF components other than "body functions" was scarcely included. Clear secular trends for individual ICF categories could not be found. Only a single IBS-specific questionnaire considered health information other than gastrointestinal symptoms.


CONCLUSIONS
Outcome assessment of clinical IBS studies is mainly based on gastrointestinal symptoms. The assessment of other health aspects like comorbid psychological symptoms or social consequences of the disease seems to be similarly important and should be considered in future trials. This would also facilitate the understanding of IBS as a biopsychosocial health condition, both in matters of aetiology and consequences.
Schönrich
S
S
Spa Medicine Research Institute Bad Elster, Germany.
Brockow
T
T
Franke
T
T
Dembski
R
R
Resch
K L
KL
Cieza
A
A
D000203:Activities of Daily Living; D002986:Clinical Trials as Topic / Q000706:statistics & numerical data*; D004185:Disability Evaluation; D006305:Health Status Indicators; D006801:Humans; D038801:International Classification of Diseases; D038622:Internationality; D043183:Irritable Bowel Syndrome / Q000175:diagnosis* / Q000453:epidemiology*; D017063:Outcome Assessment, Health Care / Q000379:methods* / Q000706:statistics & numerical data*; D011379:Prognosis; D039781:PubMed; D020127:Recovery of Function; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D016896:Treatment Outcome