Randomisation and baseline comparisons in clinical trials

Lancet. 1990 Jan 20;335(8682):149-53. doi: 10.1016/0140-6736(90)90014-v.


80 reports of randomised clinical trials in four leading general medical journals were reviewed. The reporting of the methodology of randomisation was inadequate. In 30% of trials there was no clear evidence that the groups had been randomised. Among trials that used simple randomisation the sample sizes in the two groups were too often similar, and there was an unexpected small bias in favour of there being fewer patients in the experimental group. The handling of comparisons of baseline characteristics was inadequate in 41% of the trials. Suggestions are made for improving standards.

Publication types

  • Comparative Study
  • Meta-Analysis

MeSH terms

  • Bias
  • Double-Blind Method
  • Meta-Analysis as Topic
  • Prognosis
  • Randomized Controlled Trials as Topic / methods*
  • Randomized Controlled Trials as Topic / standards
  • Research Design / standards*