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

Abstract

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 and1995. 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.

The effect of patient choice of intervention on health outcomes

“…Before initial contact, women meeting the eligibility criteria were randomly assigned to receive a recruitment script for either the No Choice or the Choice arms of the study. Using an allocation concealment protocol [10] and a randomnumbers table to prepare sequentially numbered and sealed envelopes, the study coordinator randomized women meeting the study criteria to either the No Choice or Choice Arm. Potential subjects were randomized in a 55/45 No Choice arm versus Choice arm [11] ratio to account for potentially greater participation from women given a choice.…”

Quality of randomised trials in COPD

“…A limitation of our study is that we could only assess the reporting of important markers of internal validity but not what the investigators actually did. Although the reporting and the actual quality of trials correlate it is also possible that some misclassification occurred [14][15][16][17]. Furthermore, we limited the main analysis to three aspects of internal validity and did not consider other important sources of bias, such as masking of patients.…”

La recherche clinique entre industrie et médecins

“…Les méthodes utilisées pour obtenir ces résultats favorables sont parfois décelables en comparant le protocole de l'étude avec la publication finale. C'est ainsi, par exemple, que dans 11 paires sur 62 analysées, les données étaient systématiquement identiques, alors que dans les autres elles étaient souvent modifiées en faveur de la substance du sponsor [15][16][17].…”

“…Les méthodes utilisées pour obtenir ces résultats favorables sont parfois décelables en comparant le protocole de l'étude avec la publication finale. C'est ainsi, par exemple, que dans 11 paires sur 62 analysées, les données étaient systématiquement identiques, alors que dans les autres elles étaient souvent modifiées en faveur de la substance du sponsor [15][16][17].Des résumés de congrès rapportent souvent des risques relatifs et des rapports de cote (odds-ratios) significatifs, alors qu'en réalité ces calculs très pré-liminaires sont souvent erronés. De tels résultats ne devraient pas être acceptés sans revue de la publication intégrale [18].…”