A new form of meta-analysis for combining results from randomized clinical trials and medical-practice databases.

Cross-design synthesis is a new (and still evolving) strategy for providing quantitative results that capture the strengths and minimize the weaknesses of different kinds of research. The strategy, which is being developed to answer questions about the effects of treatment in medical practice, includes (a) identifying complementary research designs and studies conducted according to those designs; (b) completing an in-depth assessment of each study with respect to the chief potential bias(es) that are associated with its design; (c) making "secondary adjustments" of study results to correct known biases; and (d) developing synthesis frameworks and models that will minimize the impact of hidden biases.