Prevention of treatment, quality improvement

• ■ Random allocation of participants to interventions

• ■ Outcome measures of known or probable clinical importance

Diagnosis

• ■ Inclusion of a spectrum of participants, some (but not all) of whom have the disorder or derangement of interest

• ■ Each participant must receive the new test and the diagnostic standard test

• ■ Either an objective diagnostic standard or a contemporary clinical diagnostic standard with demonstrably reproducible criteria for any subjectively interpreted component

• ■ Interpretation of the test without knowledge of the diagnostic standard result

• ■ Interpretation of the diagnostic standard without knowledge of the test result

Prognosis

• ■ An inception cohort of persons, all initially free of the outcome of interest

• ■ Follow-up of >80% of patients until the occurrence of either a major study end point or the end of the study

Causation

• ■ Observations concerning the relation between exposures and putative clinical outcomes

• ■ Prospective data collection with clearly identified comparison group(s) for those at risk for the outcome of interest (in descending order of preference from randomised controlled trials, quasi-randomised controlled trials, nonrandomised controlled trials, cohort studies with case by case matching or statistical adjustment to create comparable groups, to nested case-control studies)

• ■ Masking of observers of outcomes to exposures (this criterion is assumed to be met if the outcome is objective)

Economics of healthcare programmes or interventions

• ■ The economic question must compare alternative courses of action in real or hypothetical patients

• ■ The alternative diagnostic or therapeutic services or quality improvement strategies must be compared on the basis of both the outcomes they produce (effectiveness) and the resources they consume (costs)

• ■ Evidence of effectiveness must come from a study (or studies) that meets criteria for diagnosis, treatment, quality assurance, or review articles

• ■ Results should be presented in terms of the incremental or additional costs and outcomes incurred and a sensitivity analysis should be done

Clinical prediction guides

• ■ The guide must be generated in 1 set of patients (training set) and validated in an independent set of real not hypothetical patients (test set), and must pertain to treatment, diagnosis, prognosis, or causation

Differential diagnosis

• ■ A cohort of patients who present with a similar, initially undiagnosed but reproducibly defined clinical problem

• ■ Clinical setting is explicitly described

• ■ Ascertainment of diagnosis for >80% of patients using a reproducible diagnostic workup strategy and follow-up until patients are diagnosed or follow-up of >1 month for acute disorders or >1 year for chronic or relapsing disorders

Systematic reviews

• ■ The clinical topic being reviewed must be clearly stated; there must be a description of how the evidence on this topic was tracked down, from what sources, and with what inclusion and exclusion criteria

• ■ >1 article included in the review must meet the above-noted criteria for treatment, diagnosis, prognosis, causation, quality improvement, or the economics of healthcare programmes

Articles meeting the criteria set out above and chosen for coverage in Evidence-Based Medicine are described and reviewed by an expert in the content area covered by the article. This expert writes a commentary in which she or he describes the article and compares the study findings to previous research findings, identifies any important methodological problems that affect interpretation of the study results, and offers recommendations for clinical application.