[Clinical studies in rehabilitation research--problems and solutions from biometrical perspective]

Methodology of clinical studies is highly sophisticated in drug research. But clinical trials are also necessary to demonstrate efficacy and safety of rehabilitation treatment. The call for evidence based medicine has also reached rehabilitation. However, in rehabilitation medicine it is much more difficult to design and conduct clinical trials with a high methodological standard. Among the reasons are: A comparable control group is necessary because spontaneous healing and unspecific measures contribute to therapeutic success, too. But what could "placebo rehabilitation" look like? The masking of therapies (blinded studies) will hardly ever be possible. Therefore, it is more difficult to achieve the same treatment and observation for the treatment and control group. Treatments in rehabilitation take longer to become effective than a drug and maybe the success will disappear after some time. Therefore, long-term trials and follow-ups are necessary. Such studies are expensive, need a strong organisation, and drop-outs are unavoidable. An appropriate outcome variable does not always exist. "Return to work" is an important, reliable and valid variable, but it delivers only one bit of information per patient. As a consequence, smaller progress in rehabilitation can only be demonstrated with large sample sizes. Outcome variables based on time enable studies with reasonable sample sizes. Sometimes it is more difficult to obtain acceptance of randomisation in rehabilitation patients than in acute patients. Some rehabilitation hospitals have only recently begun to take an interest in controlled clinical trials, hence are not so experienced. Nevertheless, controlled clinical trials delivering convincing results are possible in rehabilitation medicine as well. But biometrical consultation is necessary e.g. for study design, study conduction and evaluation. Most important points are the methodology of the study design and its practicability. Especially in these topics rehabilitation physicians and biometrician have to cooperate.