Article

Impact of allocation concealment on conclusion drawn from meta-analyses of randomized trials

IT University of Copenhagen, København, Capital Region, Denmark
International Journal of Epidemiology (Impact Factor: 9.18). 09/2007; 36(4). DOI: 10.1093/ije/dym087
Source: OAI

ABSTRACT

Background Randomized trials without reported adequate allocation concealment have been shown to overestimate the benefit of experimental interventions. We investigated the robustness of conclusions drawn from meta-analyses to exclusion of such trials. Material Random sample of 38 reviews from The Cochrane Library 2003, issue 2 and 32 other reviews from PubMed accessed in 2002. Eligible reviews presented a binary effect estimate from a meta-analysis of randomized controlled trials as the first statistically significant result that supported a conclusion in favour of one of the interventions. Methods We assessed the methods sections of the trials in each included meta-analysis for adequacy of allocation concealment. We replicated each meta-analysis using the authors' methods but included only trials that had adequate allocation concealment. Conclusions were defined as not supported if our result was not statistically significant. Results Thirty-four of the 70 meta-analyses contained a mixture of trials with unclear or inadequate concealment as well as trials with adequate allocation concealment. Four meta-analyses only contained trials with adequate concealment, and 32, only trials with unclear or inadequate concealment. When only trials with adequate concealment were included, 48 of 70 conclusions (69%; 95% confidence interval: 56–79%) lost support. The loss of support mainly reflected loss of power (the total number of patients was reduced by 49%) but also a shift in the point estimate towards a less beneficial effect. Conclusion Two-thirds of conclusions in favour of one of the interventions were no longer supported if only trials with adequate allocation concealment were included.

Download full-text

Full-text

Available from: Karsten Juhl Jørgensen, Jun 24, 2014
    • "Mit dieser Methode wird demnach der Gefahr einer Verzerrung von Studienergebnissen entgegen gewirkt. Mittlerweile ist auch bekannt, dass ganze Schlussfolgerungen von Meta-Analysen falsch sein können , wenn Studien ohne randomisierten Zuordnungsprozess eingeschlossen werden (Pildal et al. 2007), dies muss jedoch nicht zwangsweise der Fall sein (Torgerson 2007). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Reading disabilities are one of the most frequently observed learning disorders with a prevalence ranging from 3 to 8 %. The significant impairment in the acquisition of reading skills is often associated with psychosocial stress and has a high persistence if the children and adolescents with the disability are not adequately treated. Therefore, the implementation of evidence-based interventions is critically needed. There are several treatment approaches and standardized interventions promising an improvement in reading skills of children and adolescents with reading disorders. Recently conducted meta-analyses illustrate how different kinds of treatment approaches affect reading abilities. Based on the insights of the meta-analyses, this review links evidence-based treatment approaches to standardized interventions from the German speaking area. Interventions that foster the internalization of letter-sound-correspondences and involve blending or segmenting phonemes, syllables or morphemes are based on evidence-based treatment approaches. In contrast, auditory, medical, optometric and alternative medical methods are applied without any evidence.
    No preview · Article · Aug 2015 · Zeitschrift für Erziehungswissenschaft
  • Source
    • "We extracted data on the effect of self-management interventions on health care utilisation and total costs. To assess study quality, we chose a dichotomous measure based on allocation concealment, as this is consistently associated with treatment effect [20, 21]. Allocation concealment was judged as adequate or inadequate according to the Cochrane risk of bias tool. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Background: There is increasing interest in the role of 'self-management' interventions to support the management of long-term conditions in health service settings. Self-management may include patient education, support for decision-making, self-monitoring and psychological and social support. Self-management support has potential to improve the efficiency of health services by reducing other forms of utilisation (such as primary care or hospital use), but a shift to self-management may lead to negative outcomes, such as patients who feel more anxious about their health, are less able to cope, or who receive worse quality of care, all of which may impact on their health and quality of life. We sought to determine which models of self-management support are associated with significant reductions in health services utilisation without compromising outcomes among patients with long-term conditions. Methods: We used systematic review with meta-analysis. We included randomised controlled trials in patients with long-term conditions which included self-management support interventions and reported measures of service utilisation or costs, as well as measures of health outcomes (standardized disease specific quality of life, generic quality of life, or depression/anxiety).We searched multiple databases (CENTRAL, CINAHL, Econlit, EMBASE, HEED, MEDLINE, NHS EED and PsycINFO) and the reference lists of published reviews. We calculated effects sizes for both outcomes and costs, and presented the results in permutation plots, as well as conventional meta-analyses. Results: We included 184 studies. Self-management support was associated with small but significant improvements in health outcomes, with the best evidence of effectiveness in patients with diabetic, respiratory, cardiovascular and mental health conditions. Only a minority of self-management support interventions reported reductions in health care utilisation in association with decrements in health. Evidence for reductions in utilisation associated with self-management support was strongest in respiratory and cardiovascular problems. Studies at higher risk of bias were more likely to report benefits. Conclusions: Self-management support interventions can reduce health service utilization without compromising patient health outcomes, although effects were generally small, and the evidence was strongest in respiratory and cardiovascular disorders. Further work is needed to determine which components of self-management support are most effective.
    Full-text · Article · Aug 2014 · BMC Health Services Research
  • Source
    • "Randomization tries to secure that known and unknown determining factors are spread equally across groups. Research has shown that when meta-analyses include studies whose allocation concealment is inadequate, effects of interventions can be misjudged[54]. Each study that was included in our analysis was randomized, but due to missing methodological specifications the quality of randomization procedures could not be determined. "

    Full-text · Article · Aug 2014 · PLoS ONE
Show more