Are sample sizes of randomized clinical trials in rheumatoid arthritis too large?
Author(s): Celik S(1), Yazici Y, Yazici H.
Affiliation(s): Author information:
(1)Division of Rheumatology, NYU Hospital for Joint Diseases, New York, NY, USA.
Publication date & source: 2014, Eur J Clin Invest. , 44(11):1034-44
OBJECTIVE: We had the impression that randomized clinical trials (RCTs)
frequently over enrolled patients. Thus, we surveyed power calculations in
publications of RCTs of biologics in rheumatoid arthritis (RA) to assess over
enrollment.
METHODS: A PubMed search identified 40 reports of original RCTs testing the
efficacy of infliximab, etanercept, adalimumab, abatacept, rituximab and
tocilizumab in patients with RA. As a first analysis, based on a two equal arms
study with an alpha error of 0·05 and a power of 80% and of 90%, recalculation of
the sample size was performed using the primary outcome results. In the second
analysis, only those studies with equal number of patients in both arms and also
in which all elements of a power calculation were given, were considered. New
sample sizes were calculated based on the presented power elements in the related
publications.
RESULTS: In the first analysis, when we assigned a power of 80% and of 90%, 32 of
40 (80%) studies enrolled more than required number of patients, with a mean 131
± 147 (SD), and 31 of 40 (78%) studies having had enrolled extra patients, with a
mean 121 ± 147 (SD) in their treatment arms, respectively. Eleven studies
qualified for the second analysis. There were still more patients with a mean of
48 ± 30 (SD) extra patients enrolled in the treatment arms.
CONCLUSION: Most RCTs in RA enrol more patients than needed. This is costly and
has the immediate consequence of exposing needless number of patients to
potential harm.
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