Evidence from non-randomized and partially randomized studies (N: Non-randomized)

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Randomized controlled trials (RCTs) are regarded to be the gold standard for the comparison of treatments in clinical trials. Nevertheless, the discussion about evidence from observational or partially randomized studies is still a current topic for various reasons. In some situations a randomization is not possible, feasible, or not enforceable. Another argument concerns the external validity. While a random assignment to treatment ensures internal validity of the comparison of the treatments, an assessment of external validity can best be achieved by comparing the randomized study sample to the population of patients who did not consent to randomization but met all other eligibility criteria. These considerations have led to the foundation of the 'Non-randomized Studies Methods Group' of the Cochrane Collaboration whose main task is the production of guidance on the inclusion of non-randomized studies in systematic reviews. This shows that research in this area is indicated. In the absence of evidence from RCTs it is natural to seek evidence from non-randomized or partially randomized studies. In this project, we focus on the one hand on the assessment of approaches introduced to gain for evidence from such studies and on the other hand on the development of innovative statistical methods with special emphasis on their practical applicability.