Objective: The aim of this study was to assess whether funding and the disease area are related to the internal validity of hepatobiliary randomized clinical trials.
Methods: We gathered data on funding, disease area, methodological quality (randomization and double blinding), and sample size from 616 hepatobiliary randomized clinical trials published from 1985 to 1996 in 12 MEDLINE indexed journals.
Results: The internal validity (methodological quality and sample size) of trials funded by profit or nonprofit organizations was not significantly different. Compared with these trials, trials without funding were significantly less likely to report adequate generation of the allocation sequence (55% vs 41%, p = 0.001) and to be double blind (42% vs 25%, p < 0.001), but the proportion with adequate allocation concealment and the sample size were not significantly different. The trials covered 12 disease areas. The proportion of funded trials did not differ significantly in different disease areas. The disease area was significantly associated with the proportion of trials with adequate generation of the allocation sequence (p < 0.001), allocation concealment (p = 0.003), and double blinding (p < 0.001) as well as the sample size (p < 0.001). This association was not explained by the proportion of trials with funding.
Conclusions: External funding was significantly associated with adequate methodological quality, but not with the sample size. Irrespective of funding, the disease area was significantly associated with the methodological quality and sample size. Accordingly, external funding and the disease area are significant predictors of the internal validity of hepatobiliary randomized clinical trials.