Using the proper summary/descriptive statistics is essential. Although investigators may use standard deviations and standard errors interchangeably, the standard deviation is appropriate as a descriptive summary, whereas the standard error is intended to convey the uncertainty of an estimate (such as the mean). Confidence intervals are more informative than significance levels and p-values.
Reports of clinical trials usually do not distinguish between clinical significance and statistical significance - but they should. Clinical significance can be expressed in terms of the magnitude and direction of treatment effects or differences. Although this is important for superiority trials, it is even more important for equivalence and non-inferiority trials.
Some journals require structured titles and abstracts because they are the only part of many reports that some readers examine. Therefore, the abstract becomes very important - in the medical literature the abstract is critical. A good abstract for the report of a clinical trial includes objectives, design, setting or types of practices, characteristics of the study population, interventions used, primary outcome measurements, principal results, and conclusions. Abstracts should be no longer than 250 words and usually do not include descriptions of the statistical methods.
The reports for treatment mechanism and dose-finding studies (Phase I) should include information about study design, demographics, toxicity and side effects, and recommendations for later trials. The objectives of safety and efficacy studies (Phase II) are to demonstrate treatment feasibility, estimate treatment success, estimate treatment complications, and facilitate informal comparisons with other therapies that might motivate comparative trials.
With respect to the latter objective, the report should recognize the potential for strong selection bias and avoid overly-enthusiastic statements about relative efficacy. The reports for safety and efficacy studies should consist of the following outline:
- study design
- study setting
- outcome measures
- statistical methods
- discussion and conclusions