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Direct evidence comes from research that directly compares the interventions in which we are interested when applied to the populations in which we are interested and measures outcomes important to patients. Evidence can be indirect in one of four ways. First, patients may differ from those of interest (the term applicability is often used for this form of indirectness). Second, the intervention tested may differ from the intervention of interest. Decisions regarding indirectness of patients and interventions depend on an understanding of whether biological or social factors are sufficiently different that one might expect substantial differences in the magnitude of effect. Third, outcomes may differ from those of primary interest - for instance, surrogate outcomes that are not themselves important, but measured in the presumption that changes in the surrogate reflect changes in an outcome important to patients. A fourth type of indirectness, which is conceptually different from the first three, occurs when clinicians must choose between interventions that have not been tested in head to head comparisons. Making comparisons between treatments under these circumstances requires specific statistical methods and will be rated down in quality by one or two levels depending on the extent of differences between the patient populations, co-interventions, measurements of the outcome, and the methods of the trials of the candidate interventions against some other comparator., (Copyright © 2012. Published by Elsevier GmbH.)

The patient-relevant benefit of diagnostic tests should be evaluated; addressing diagnostic accuracy alone is not sufficient, though. Several phased evaluation schemes for diagnostic tests have been proposed in the literature. They all have in common that studies evaluating the effect on patient outcome have a central position. Various designs are available to evaluate the effect of a diagnostic test on patient outcome. Five design options are presented and their pros and cons discussed. Indeed, such studies are feasible. Under exceptional conditions, however, it may be sufficient to base evaluation on diagnostic accuracy studies combined with further information (mostly from treatment trials)., (Copyright © 2011. Published by Elsevier GmbH.)