Comparison of evidence of treatment effects in randomized and nonrandomized studies
| dc.contributor.author | Ioannidis, J. P. | en |
| dc.contributor.author | Haidich, A. B. | en |
| dc.contributor.author | Pappa, M. | en |
| dc.contributor.author | Pantazis, N. | en |
| dc.contributor.author | Kokori, S. I. | en |
| dc.contributor.author | Tektonidou, M. G. | en |
| dc.contributor.author | Contopoulos-Ioannidis, D. G. | en |
| dc.contributor.author | Lau, J. | en |
| dc.date.accessioned | 2015-11-24T19:28:38Z | |
| dc.date.available | 2015-11-24T19:28:38Z | |
| dc.identifier.issn | 0098-7484 | - |
| dc.identifier.uri | https://olympias.lib.uoi.gr/jspui/handle/123456789/22913 | |
| dc.rights | Default Licence | - |
| dc.subject | *Clinical Trials as Topic | en |
| dc.subject | Data Interpretation, Statistical | en |
| dc.subject | *Evidence-Based Medicine | en |
| dc.subject | Humans | en |
| dc.subject | *Meta-Analysis as Topic | en |
| dc.subject | *Randomized Controlled Trials as Topic | en |
| dc.title | Comparison of evidence of treatment effects in randomized and nonrandomized studies | en |
| heal.abstract | CONTEXT: There is substantial debate about whether the results of nonrandomized studies are consistent with the results of randomized controlled trials on the same topic. OBJECTIVES: To compare results of randomized and nonrandomized studies that evaluated medical interventions and to examine characteristics that may explain discrepancies between randomized and nonrandomized studies. DATA SOURCES: MEDLINE (1966-March 2000), the Cochrane Library (Issue 3, 2000), and major journals were searched. STUDY SELECTION: Forty-five diverse topics were identified for which both randomized trials (n = 240) and nonrandomized studies (n = 168) had been performed and had been considered in meta-analyses of binary outcomes. DATA EXTRACTION: Data on events per patient in each study arm and design and characteristics of each study considered in each meta-analysis were extracted and synthesized separately for randomized and nonrandomized studies. DATA SYNTHESIS: Very good correlation was observed between the summary odds ratios of randomized and nonrandomized studies (r = 0.75; P<.001); however, nonrandomized studies tended to show larger treatment effects (28 vs 11; P =.009). Between-study heterogeneity was frequent among randomized trials alone (23%) and very frequent among nonrandomized studies alone (41%). The summary results of the 2 types of designs differed beyond chance in 7 cases (16%). Discrepancies beyond chance were less common when only prospective studies were considered (8%). Occasional differences in sample size and timing of publication were also noted between discrepant randomized and nonrandomized studies. In 28 cases (62%), the natural logarithm of the odds ratio differed by at least 50%, and in 15 cases (33%), the odds ratio varied at least 2-fold between nonrandomized studies and randomized trials. CONCLUSIONS: Despite good correlation between randomized trials and nonrandomized studies-in particular, prospective studies-discrepancies beyond chance do occur and differences in estimated magnitude of treatment effect are very common. | en |
| heal.access | campus | - |
| heal.fullTextAvailability | TRUE | - |
| heal.identifier.secondary | http://www.ncbi.nlm.nih.gov/pubmed/11497536 | - |
| heal.journalName | JAMA | en |
| heal.journalType | peer-reviewed | - |
| heal.language | en | - |
| heal.publicationDate | 2001 | - |
| heal.recordProvider | Πανεπιστήμιο Ιωαννίνων. Σχολή Επιστημών Υγείας. Τμήμα Ιατρικής | el |
| heal.type | journalArticle | - |
| heal.type.el | Άρθρο Περιοδικού | el |
| heal.type.en | Journal article | en |
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