An evaluation of the quality of clinical trials in anesthesia

Background: The authors evaluated the quality of clinical trials published in four anesthesia journals during the 20-yr period from 1981-2000. Methods: Trials published in four major anesthesia journals during the peri ods 1981-1985, 1991-1995, and the first 6 months of 2000 were grouped accor ding to journal and year. Using random number tables, four trials were sele cted from all of the eligible clinical trials in each journal in each year for the periods 1981-1985 and 1991-1995, and five trials were selected from all of the trials in each journal in the first 6 months of 2000. Methods a nd results sections from the 160 trials from 1981-1985 and 1991-1995 were r andomly ordered and distributed to three of the authors for blinded review of the quality of the study design according to 10 predetermined criteria ( weighted equally, maximum score of 10): informed consent and ethics approva l, eligibility criteria, sample size calculation, random allocation, method of randomization, blind assessment of outcome, adverse outcomes, statistic al analysis, type I error, and type II error. After these trials were evalu ated, 20 trials from the first 6 months of 2000 were randomly ordered, dist ributed, and evaluated as described. Results. The mean ( SD) analysis scores pooled for the four journals increa sed from 5.5 +/- 1.4 in 1981-1985 to 7.0 +/- 1.1 in 1991-1995 (P < 0.00001) and to 7.8 +/- 1.5 in 2000. For 7 of the 10 criteria, the percentage of tr ials from the four journals that fulfilled the criteria increased significa ntly between 1981-1985 and 1991-1995. During the 20-yr period, the reportin g of sample size calculation and method of randomization increased threefol d to fourfold, whereas the frequency of type I statistical errors remained unchanged. Conclusion. Although the quality of clinical trials in four major anesthesi a journals has increased steadily during the past two decades, specific are as of trial methodology require further attention.