Influence of reported study design characteristics on intervention effect estimates from randomized, controlled trials.

Published evidence suggests that aspects of trial design lead to biased intervention effect estimates, but findings from different studies are inconsistent. This study combined data from 7 meta-epidemiologic studies and removed overlaps to derive a final data set of 234 unique meta-analyses containing 1973 trials. Outcome measures were classified as "mortality," "other objective," "or subjective," and Bayesian hierarchical models were used to estimate associations of trial characteristics with average bias and between-trial heterogeneity. Intervention effect estimates seemed to be exaggerated in trials with inadequate or unclear (vs. adequate) random-sequence generation (ratio of odds ratios, 0.89 [95% credible interval {CrI}, 0.82 to 0.96]) and with inadequate or unclear (vs. adequate) allocation concealment (ratio of odds ratios, 0.93 [CrI, 0.87 to 0.99]). Lack of or unclear double-blinding (vs. double-blinding) was associated with an average of 13% exaggeration of intervention effects (ratio of odds ratios, 0.87 [CrI, 0.79 to 0.96]), and between-trial heterogeneity was increased for such studies (SD increase in heterogeneity, 0.14 [CrI, 0.02 to 0.30]). For each characteristic, average bias and increases in between-trial heterogeneity were driven primarily by trials with subjective outcomes, with little evidence of bias in trials with objective and mortality outcomes. This study is limited by incomplete trial reporting, and findings may be confounded by other study design characteristics. Bias associated with study design characteristics may lead to exaggeration of intervention effect estimates and increases in between-trial heterogeneity in trials reporting subjectively assessed outcomes.

Development of a combined database for meta-epidemiological research.

Collections of meta-analyses assembled in meta-epidemiological studies are used to study associations of trial characteristics with intervention effect estimates. However, methods and findings are not consistent across studies. To combine data from 10 meta-epidemiological studies into a single database, and derive a harmonized dataset without overlap between meta-analyses. The database design allowed trials to be contained in different meta-analyses, multiple meta-analyses in systematic reviews, overlapping meta-analyses between systematic reviews, and multiple references to the same trial or review. Unique identifiers were assigned to each reference and used to identify duplicate trials. Sets of meta-analyses with overlapping trials were identified and duplicates removed. Overlapping trials were used to examine agreement between assessments of trial characteristics. The combined database contained 427 reviews, 454 meta-analyses and 4874 trial results. Of these, 258 meta-analyses were unique, while for 196 at least one trial overlapped with another meta-analysis. Median kappa statistics for reliability of assessments were 0.60 for sequence generation, 0.58 for allocation concealment and 0.87 for blinding. Based on inspection of sets of overlapping meta-analyses, 91 meta-analyses containing 1344 trial results were removed. Additionally, 24 duplicated trial results were removed from 16 meta-analyses, to derive a final database containing 363 meta-analyses and 3477 unique trial results. The final database will be used to examine the combined evidence on sources of bias in randomized controlled trials. The strategy used to remove overlap between meta-analyses may be of use for future empirical research. Copyright © 2010 John Wiley & Sons, Ltd.

Reporting on blinding in trial protocols and corresponding publications was often inadequate but rarely contradictory.

OBJECTIVE: To compare the reporting on blinding in protocols and articles describing randomized controlled trials. STUDY DESIGN AND SETTING: We studied 73 protocols of trials approved by the scientific/ethical committees for Copenhagen and Frederiksberg, 1994 and 1995, and their corresponding publications. RESULTS: Three out of 73 trials (4%) reported blinding in the protocol that contradicted that in the publication (e.g., "open" vs. "double blind"). The proportion of "double-blind" trials with a clear description of the blinding of participants increased from 11 out of 58 (19%) when based on publications alone to 39 (67%) when adding the information in the protocol. The similar proportions for the blinding of health care providers were 2 (3%) and 22 (38%); and for the blinding of data collectors, they were 8 (14%) and 14 (24%). In 52 of 58 publications (90%), it was unclear whether all patients, health care providers, and data collectors had been blinded. In 4 of the 52 trials (7%), the protocols clarified that all three key trial persons had been blinded. CONCLUSIONS: The reporting on blinding in both trial protocols and publications is often inadequate. We suggest developing international guidelines for the reporting of trial protocols and public access to protocols.

Comparison of descriptions of allocation concealment in trial protocols and the published reports: cohort study.

OBJECTIVES: To compare how allocation concealment is described in publications of randomised clinical trials and corresponding protocols, and to estimate how often trial publications with unclear allocation concealment have adequate concealment according to the protocol. DESIGN: Cohort study of 102 sets of trial protocols and corresponding publications. SETTING: Protocols of randomised trials approved by the scientific and ethical committees for Copenhagen and Frederiksberg, 1994 and 1995. MAIN OUTCOME MEASURES: Frequency of adequate, unclear, and inadequate allocation concealment and sequence generation in trial publications compared with protocols, and the proportion of protocols where methods were reported to be adequate but descriptions were unclear in the trial publications. RESULTS: 96 of the 102 trials had unclear allocation concealment according to the trial publication. According to the protocols, 15 of these 96 trials had adequate allocation concealment (16%, 95% confidence interval 9% to 24%), 80 had unclear concealment (83%, 74% to 90%), and one had inadequate concealment. When retrospectively defined loose criteria for concealment were applied, 83 of the 102 trial publications had unclear concealment. According to their protocol, 33 of these 83 trials had adequate allocation concealment (40%, 29% to 51%), 49 had unclear concealment (59%, 48% to 70%), and one had inadequate concealment. CONCLUSIONS: Most randomised clinical trials have unclear allocation concealment on the basis of the trial publication alone. Most of these trials also have unclear allocation concealment according to their protocol.

Polyclonal immunoglobulin for treatment of bacterial sepsis: a systematic review.

Randomized trials of adjunctive treatment of bacterial sepsis with polyclonal immunoglobulin show conflicting results. We performed a systematic review and a meta-analysis of the results of randomized trials that compared reductions in mortality rates in patient groups treated with polyclonal immunoglobulin versus either placebo or no treatment in addition to conventional treatment. High-quality trials had adequate concealment of allocation, were double-blinded and placebo-controlled, and made data available for intention-to-treat analyses. Twenty trials were included. Meta-analysis of all trials showed a relative risk of death with immunoglobulin treatment of 0.77 (95% confidence interval [CI], 0.68-0.88). High-quality trials (involving a total of 763 patients, 255 of whom died) showed a relative risk of 1.02 (95% CI, 0.84-1.24), whereas other trials (involving a total of 948 patients, 292 of whom died) showed a relative risk of 0.61 (95% CI, 0.50-0.73). Because high-quality trials failed to demonstrate a reduction in mortality, polyclonal immunoglobulin should not be used for treatment of sepsis except in randomized clinical trials.

[Systemic and local allergy to human insulin]. / Systemisk og lokal allergi over for humant insulin.

After introduction of recombinant human insulin, immunological reactions have become rare, but symptomatic immune reactions to insulin still occur. We present four insulin-treated diabetic patients who developed hypersensitivity to insulin or additives to insulin preparations. We show that symptomatic immunological reactions to insulin have not been eliminated by the introduction of recombinant human insulin. Furthermore it demonstrates the importance of skin-biopsy-verified diagnoses and the relevance of differentiation between different types of insulin allergy.