Clinical Trials

Clinical Trials: A Practical Guide ■❚❙❘at the beginning of the trial when case report forms are being designed to capturethe data. Each piece of information should link to a data entry field(s). In a largeclinical trial, it is often necessary to undertake interim analyses of the results,to be confident that it is appropriate to continue randomizing patients betweenthe treatment arms. A large number of tables are usually constructed at this time –more than can be reported within the main published report.Once the interim report has been constructed and reviewed, it is useful to take theopportunity to decide on the content and format of the tables for publicpresentations of the results and for the final publication; this enables the finalreport to be produced speedily once the datasets are cleaned and locked up.Remember that few people are privy to the interim results (only those on the datamonitoring board) – this is a key reason for discussing the layout with emptytables. It also ensures that the focus of the results is decided upon withoutreference to the actual results obtained, which maintains objectivity. For instance,the focus is appropriately retained on the chosen main outcome measures andadverse effects, whilst also reporting the named additional outcome measures andany prespecified subgroup analyses.Once the final report is produced, the computer-generated statistical outputshould be checked. It should also be carefully reviewed for errant calculationsand to ensure that figures are displaying correct information. Consistency acrossdifferent presentations of data and different methods of analysis can also bechecked, for instance between a survival plot and the corresponding hazardratio, comparing the odds ratios over a specified time period with hazard ratios,or comparing hazard ratios with mean survival times in the two groups.Journal guidelinesJournals often specify the maximum number of tables and figures that can beincorporated in a manuscript. If they do not state this explicitly then you still needto ensure that the number is in accordance with other papers published in thatjournal. A general rule of thumb is to include no more than one table or figure per1,000 words of text [6]. Many guidelines apply to most mainstream journals,whether or not they are stated explicitly. When submitting the paper to a journal,tables should be typed in double spacing, each on a separate page with a selfexplanatorytitle. They should be placed at the end of the manuscript with theirapproximate locations indicated in the text [7]. Journals have different policies onwhether it is necessary to explain abbreviations used in a footnote when they havepreviously been used in the text.399