EVIDENCEBASED MEDICINE AND PHARMACY 1 2 Evidencebased medicine

EVIDENCE-BASED MEDICINE AND PHARMACY 1. 2. Evidence-based medicine Evidence-based pharmacy

U. S. Preventive Services Task Force (USPSTF) n n Level I: Evidence obtained from at least one properly designed randomized controlled trial. A randomized controlled trial (RCT) (or randomized control trial) is a specific type of scientific experiment, and the gold standard for a clinical trial. RCTs are often used to test the efficacy and/or effectiveness of various types of medical intervention within a patientpopulation. RCTs may also provide an opportunity to gather useful information about adverse effects, such as drug reactions.

U. S. Preventive Services Task Force (USPSTF) n n Level II-1: Evidence obtained from well-designed controlled trials without randomization. Randomization is the process of making something random; this means: n n n Generating a random permutation of a sequence (such as when shuffling cards). Selecting a random sample of a population (important in statistical sampling). Allocating experimental units via random assignment to a treatment or control condition. Generating random numbers: see Random number generation. Transforming a data stream (such as when using a scrambler in telecommunications).

U. S. Preventive Services Task Force (USPSTF) n n Level II-2: Evidence obtained from welldesigned cohort or case-control analytic studies, preferably from more than one center or research group. A cohort is a group of people who share a common characteristic or experience within a defined period (e. g. , are born, are exposed to a drug or vaccine or pollutant, or undergo a certain medical procedure). Thus a group of people who were born on a day or in a particular period, say 1948, form a birth cohort.

U. S. Preventive Services Task Force (USPSTF) n A case-control study is a type of study design used widely, often in epidemiology. It is a type of observational study in which two existing groups differing in outcome are identified and compared on the basis of some supposed causal attribute. Case-control studies are often used to identify factors that may contribute to a medical condition by comparing subjects who have that condition/disease (the "cases") with patients who do not have the condition/disease but are otherwise similar (the "controls").

U. S. Preventive Services Task Force (USPSTF) n n Level II-3: Evidence obtained from multiple time series with or without the intervention. Dramatic results in uncontrolled trials might also be regarded as this type of evidence. Level III: Opinions of respected authorities, based on clinical experience, descriptive studies, or reports of expert committees.

UK National Health Service n n Level A: Consistent Randomised Controlled Clinical Trial, cohort study, all or none (see note below), clinical decision rule validated in different populations. Level B: Consistent Retrospective Cohort, Exploratory Cohort, Ecological Study, Outcomes Research, case-control study; or extrapolations from level A studies.

UK National Health Service n n Level C: Case-series study or extrapolations from level B studies. Level D: Expert opinion without explicit critical appraisal, or based on physiology, bench research or first principles.

Categories of recommendations n In guidelines and other publications, recommendation for a clinical service is classified by the balance of risk versus benefit of the service and the level of evidence on which this information is based.

Categories of recommendations n The U. S. Preventive Services Task Force uses: n Level A: Good scientific evidence suggests that the benefits of the clinical service substantially outweigh the potential risks. Clinicians should discuss the service with eligible patients.

Categories of recommendations n n Level B: At least fair scientific evidence suggests that the benefits of the clinical service outweighs the potential risks. Clinicians should discuss the service with eligible patients. Level C: At least fair scientific evidence suggests that there are benefits provided by the clinical service, but the balance between benefits and risks are too close for making general recommendations. Clinicians need not offer it unless there are individual considerations.

Categories of recommendations n n Level D: At least fair scientific evidence suggests that the risks of the clinical service outweighs potential benefits. Clinicians should not routinely offer the service to asymptomatic patients. Level E: Scientific evidence is lacking, of poor quality, or conflicting, such that the risk versus benefit balance cannot be assessed. Clinicians should help patients understand the uncertainty surrounding the clinical service.