Clinical trials in dermatology, part 4: analysis and interpretation

Understanding and evaluating clinical trials

In this review, we attempt to provide the basic knowledge necessary to understand and evaluate clinical trials because properly conducted, randomized clinical trials are the best sources for determining the best available treatment. Other commonly used sources rarely provide sufficient detail necessary to determine the efficacy and safety of any treatment, and they often contain biases or pitfalls that make them unacceptable or unreliable. Our method for reviewing clinical trials allows a busy clinician to use his or her time most efficiently by deciding not to read the majority of poorly conceived, designed, executed, or reported trials and those trials with insignificant results. It provides a means to determine the quality of the trials that one does decide to read and to retain and retrieve the information when it is needed. The method involves recognizing and evaluating the features that strengthen clinical trials and help validate their conclusions. These features include proper selection and allocation of patients, inclusion of an appropriate control group, randomization, prior selection of clinically and biologically important outcome variables, blinding of assessment, consideration of patient compliance and drop out, and proper presentation and statistical analysis of results.

Development of anthralin short-contact therapy in psoriasis: survey of published clinical trials

In a survey of clinical trials concerning the efficacy of short-contact therapy with anthralin in psoriasis vulgaris, focusing principally on methodologic issues, twenty-four papers published between January 1982 and December 1989, in English, French, and Italian, were selected. Nine of 24 papers reported on more than one trial, giving a total of 37 clinical trials to be evaluated. A great heterogeneity was evident in many aspects of the design and conduct of these trials, making pooling of results impossible. Most trials suffered from flaws in general methodologic aspects such as randomization and blinding. Limitations in general applicability of results were discussed with reference to the popular use of self-control design and selection of composite indexes (e.g., PASI) as an outcome variable. Published trials are not a reliable guide to clinical decisions concerning short-contact therapy, and some methodologic observations we made could be of general interest in designing clinical trials of psoriasis.