Objective: The recruitment process may generate a selected patient sample, which may threaten the generalizability of trial results. This risk is particularly high in case disease and patient characteristics demonstrate a wide variation, such as in irritable bowel syndrome (IBS). We compared IBS patients who were selected, approached, and randomized to participate in a clinical trial assessing the efficacy of dietary fiber therapy in IBS.
Study design and setting: Retrospective survey in primary care patients diagnosed with IBS by their general practitioner in the past 2 years selected and invited for participation in a trial. Characteristics were compared between randomized patients (n=193) nonrandomized eligible patients (n=371), and patients not eligible for participating in the trial (n=724).
Results: Of the 2,100 IBS patients, 1,288 (61%) returned the questionnaire. Randomized patients had a higher intensity of IBS abdominal pain as compared to the other groups, a higher consultation rate and a longer IBS disease history. Noneligible patients had less active IBS symptoms.
Conclusions: Patients randomized do differ from those nonrandomized in IBS disease characteristics. These observations may have implications for the applicability of our research outcome.