Laboratory-related outcomes in healthcare.

Outcomes studies, long common on the therapeutic side of medicine, are appearing in the diagnostic arena. Outcomes can be defined as results of medical interventions (therapies or tests) in terms of health or cost. The studies of outcomes are important because funding for medical interventions increasingly depends on them; a major accrediting agency even defines "quality" entirely in terms of outcomes. The study of laboratory-related outcomes is complex. Multiple steps occur between testing and outcomes, physicians act unpredictably on test results, and outcomes studies have high costs relative to potential profit from the test. Study design often must specify the action that is to follow a test result. The model outcomes study is a randomized controlled trial (RCT). The CONSORT statement, which is used as a guideline for RCTs of therapies, is largely applicable to studies of diagnostic interventions. Recent laboratory-related RCTs have addressed questions such as: "Does routine testing before cataract surgery decrease morbidity or mortality?" and "Does fecal occult bleed testing decrease the incidence of colorectal cancer?" RCTs of tests are sometimes impractical. Other approaches include simulation modeling and the use of intervention and control periods of testing. As for RCTs, these approaches require careful attention to study design, data analysis, and interpretation and reporting of results.