Meta‐analysis: factors affecting placebo response rate in the irritable bowel syndrome
Bibliographic record
Abstract
BACKGROUND: Irritable bowel syndrome (IBS) is a functional disorder of the gastrointestinal tract with a significant placebo response. AIM: To conduct a systematic review and meta-analysis examining the magnitude of placebo response rate in treatment trials for IBS. METHODS: MEDLINE, EMBASE and the Cochrane central register of controlled trials were searched to identify randomized controlled trials (RCTs) comparing pharmacological therapies with placebo in adult IBS patients. Studies reported either global assessment of IBS symptom cure or improvement or abdominal pain cure or improvement. Data were extracted as intention-to-treat analyses with drop-outs assumed to be treatment failures and pooled using a random-effects model. Proportion of placebo patients experiencing symptom improvement or resolution was reported with a 95% confidence interval (CI). Effect of trial characteristics on magnitude of placebo response was examined. RESULTS: In all, 73 RCTs were eligible, including 8364 patients with IBS allocated to placebo. Pooled placebo response rate across all RCTs was 37.5% (95% CI 34.4-40.6%). Rates were higher in European RCTs, RCTs that used physician-reported outcomes and RCTs using shorter duration of therapy. CONCLUSIONS: Placebo response rates across RCTs of pharmacological therapies in IBS were high. Future research should identify patient characteristics predicting placebo response.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.106 | 0.230 |
| Meta-epidemiology (narrow) | 0.004 | 0.002 |
| Meta-epidemiology (broad) | 0.023 | 0.053 |
| Bibliometrics | 0.007 | 0.008 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.005 | 0.003 |
| Open science | 0.003 | 0.002 |
| Research integrity | 0.004 | 0.003 |
| Insufficient payload (model declined to judge) | 0.003 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".