Distributions of baseline categorical variables were different from the expected distributions in randomized trials...

Comparing observed and expected distributions of baseline continuous variables in randomized controlled trials (RCTs) can be used to assess publication integrity. We explored whether baseline categorical variables could also be used.

The observed and expected (binomial) distribution of all baseline categorical variables were compared in four sets of RCTs: two controls, and two with publication integrity concerns. We also compared baseline calculated and reported P-values.

The observed and expected distributions of baseline categorical variables were similar in the control datasets, both for frequency counts (and percentages) and for between-group differences in frequency counts. However, in both sets of RCTs with publication integrity concerns, about twice as many variables as expected had between-group differences in frequency counts of one or 2, and far fewer variables than expected had between-group differences of >4 (P < 0.001 for both datasets). Furthermore, about one in six reported P-values for baseline categorial variables differed by > 0.1 from the calculated P-value in trials with publication integrity concerns.

Comparing the observed and expected distributions and reported and calculated P-values of baseline categorical variables may help in the assessment of publication integrity of a body of RCTs.