What is evidence-based health care?
Evidence-based health care is the conscientious use of current best evidence in making decisions about the care of individual patients or the delivery of health services. Current best evidence is up-to-date information from relevant, valid research about the effects of different forms of health care, the potential for harm from exposure to particular agents, the accuracy of diagnostic tests, and the predictive power of prognostic factors.
Evidence-based clinical practice is an approach to decision-making in which the clinician uses the best evidence available, in consultation with the patient, to decide upon the option which suits that patient best.
Evidence-based medicine is the conscientious, explicit and judicious use of current best evidence in making decisions about the care of individual patients. The practice of evidence-based medicine means integrating individual clinical expertise with the best available external clinical evidence from systematic research.
What is a systematic review?
To help identify which forms of health care work, which do not, and which are even harmful, results from similar randomized controlled trials need to be brought together. Trials need to be assessed and those that are of good quality and unbiased can be combined to produce both a more statistically reliable result and one that can be more easily applied in other settings. This combination of trials needs to be done in as reliable a way as possible. It needs to be systematic. A systematic review uses a predefined, explicit methodology. The methods used include steps to minimize bias in all parts of the process: identifying relevant studies, selecting them for inclusion, and collecting and combining their data. Studies should be sought regardless of their results.
A systematic review does not need to contain a statistical synthesis of the results from the included studies. This might be impossible if the designs of the studies are too different for an averaging of their results to be meaningful or if the outcomes measured are not sufficiently similar. If the results of the individual studies are combined to produce an overall statistic, this is usually called a meta-analysis. A meta-analysis can also be done without a systematic review, simply by combining the results from more than one trial. However, although such a meta-analysis will have greater mathematical precision than an analysis of any one of the component trials, it will be subject to biases that arise from the study selection process, and may produce a mathematically precise, but clinically misleading, result.
What is a systematic review of diagnostic test accuracy?
Diagnostic tests aim to reduce uncertainty about an individual's condition and aid in the diagnosis and detection of disease. A plethora of tests are available for almost every condition imaginable. Many tests exist to detect the same condition and new tests are being developed all the time. A perfect test would identify all patients with the target condition, without making mistakes, but perfect tests are rare and the users of a test wish to know how well the test discriminates between individuals who have the target condition and those who have not, also known as the diagnostic test accuracy.
The accuracy of diagnostic tests is studied by comparing the results of the test under evaluation with the results of a test known to be very good (the reference standard) in the same patients/participants.
Clinicians, policymakers and patients routinely face a range of questions regarding diagnostic tests. They want to know if testing improves outcome, would like to know what test to use, to purchase or to recommend in practice guidelines, and how to interpret the results of testing. Systematic reviews can help practitioners and decision makers in answering these questions, by summarising the available evidence and helping to explain differences among studies on the same question. As with elsewhere in science, systematic reviews and meta-analyses can be used to obtain more precise estimates, when small studies addressing the same test and study participant types in the same setting are summarised. This combination of studies needs to be done in as reliable a way as possible. For this reason, it needs to be systematic. Systematic reviews of test accuracy use a predefined and explicit methodology.
Accuracy measures the ability of the test to distinguish between persons with and without the target condition. Good accuracy is desirable but is not the only information required to assess the effectiveness of a diagnostic test. To show that one test does more good than harm in terms of patient outcomes, one may require randomized controlled trials of test and treatment strategies.
Systematic reviews of diagnostic test accuracy are powerful tools for producing reliable and precise measures of the accuracy of a test for specific patient/participant group and setting. Systematic reviews and meta analyses of test accuracy may be the preferred source of such evidence, but building reviews and summarizing study results can be methodologically challenging. The information obtained from these reviews is useful for assessing the accuracy of a test or tests but evidence from randomized controlled trials of combined 'test and treatment' strategies, and reviews of such studies, are needed to assess the effects of tests on patient outcomes.
What is The Cochrane Collaboration?
The Cochrane Collaboration is an international not-for-profit and independent organization, dedicated to making up-to-date, accurate information about the effects of health care readily available worldwide. It produces and disseminates systematic reviews of healthcare interventions and promotes the search for evidence in the form of clinical trials and other studies of interventions. The Cochrane Collaboration was founded in 1993 and named after the British epidemiologist, Archie Cochrane.