Evidence-Based Medicine

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Case series It is a report on a series of patients with an outcome of interest. No control group is involved. Case series provide weaker evidence than case control studies. Clinical Practice Guideline Is a systematically developed statement designed to assist practitioners and patient make decisions about appropriate health care for specific clinical circumstances. Cluster randomisation A cluster randomised study is one in which a group of participants are randomised to the same intervention together. Examples of cluster randomisation include allocating together people in the same village, hospital, or school. If the results are then analysed by individuals rather than the group as a whole bias can occur. The unit of randomisation should be the same as the unit of analysis. Often a cluster randomised trial answers a different question from one randomised by individuals. An intervention at the level of the village or primary care practice may well have a different effect from one at the level of an individual patient. Therefore, trying to compensate by allowing for intra class correlation coefficients or some other method may not be appropriate. Cohort study Involves identification of two groups (cohorts) of patients, one which did receive the exposure of interest, and one which did not, and following these cohorts forward for the outcome of interest. Exposure is likely to cause specified events (e.g. lung cancer). Prospective cohort studies (which track participants forward in time) are more reliable than retrospective cohort studies. Cohort study is a non-experimental study design that follows a group of people (a cohort), and then looks at how events differ among people within the group. A study that examines a cohort, which differs in respect to exposure to some suspected risk factor (e.g. smoking), is useful for trying to ascertain whether exposure is likely to cause specified events (e.g. lung cancer). Prospective cohort studies (which track participants forward in time) are more reliable than retrospective cohort studies. -30-
Cohort studies should not be included within the Benefits section, unless it is not reasonable to expect higher levels of evidence. Completer analysis Analysis of data from only those participants who remained at the end of the study. Compare with intention to treat analysis, which uses data from all participants who enrolled. Confidence interval (CI) An estimate of precision. If a study is repeated 100 times, the results will fall within this range 95 times; the CI quantifies the uncertainty in measurement; usually reported as 95% CI, which is the range of values within which we can be 95% sure that the true value for the whole population lies. The 95% confidence interval (or 95% confidence limits) would include 95% of results from studies of the same size and design in the same population. This is close but not identical to saying that the true size of the effect (never exactly known) has a 95% chance of falling within the confidence interval. If the 95% confidence interval for a relative risk (RR) or an odds ratio (OR) crosses 1, then this is taken as no evidence of an effect. The practical advantages of a confidence interval (rather than a P value) is that they present the range of likely effects. Controlled clinical trial (CCT) A trial in which participants are assigned to two or more different treatment groups. In BMJ Clinical <strong>Evidence</strong>, we use the term to refer to controlled trials in which treatment is assigned by a method other than random allocation. When the method of allocation is by random selection, the study is referred to as a randomised controlled trial (RCT; see below). Non-randomised controlled trials are more likely to suffer from bias than RCTs. Controls In a randomised controlled trial (RCT), controls refer to the participants in its comparison group. They are allocated either to placebo, no treatment, or a standard treatment. Correlation coefficient A measure of association that indicates the degree to which two variables change together in a linear relationship. It is represented by r, and varies -31-
Page 1 and 2: Highlights On Evidence-Based Medici
Page 3 and 4: -3-
Page 5 and 6: Index Contents Page No. - Preface t
Page 7 and 8: Preface to the Sixth Edition Praise
Page 9 and 10: EVIDENCE-BASED MEDICINE Introductio
Page 11 and 12: The practice of evidence-based medi
Page 13 and 14: A systematic review is a critical a
Page 15 and 16: Strength of Recommendation Taxonomy
Page 17 and 18: TABLE 2. Assessing Quality of Evide
Page 19 and 20: Strength of Recommendation Based on
Page 21 and 22: In order to obtain the best evidenc
Page 23 and 24: The following are all common source
Page 25 and 26: (Suggestive Guideline) STRATEGIC PL
Page 27 and 28: GLOSSARY OF TERMS IN EVIDENCE-BASED
Page 29: 9. Where the condition is acute and
Page 33 and 34: Crossver-sectional Study The observ
Page 35 and 36: Experimental study A study in which
Page 37 and 38: I Incidence The number of new cases
Page 39 and 40: until the clinician and patient are
Page 41 and 42: O Observational studies Observation
Page 43 and 44: patients. POEMs are selected from r
Page 45 and 46: Prevalence The proportion of people
Page 47 and 48: Relative risk (RR) The number of ti
Page 49 and 50: Standardised mean difference (SMD)
Page 51 and 52: W Weighted mean difference (WMD) A
Page 53 and 54: Evidence-Based Medicine Resources A
Page 55 and 56: (with ACP Journal Club). The Cochra
Page 57 and 58: C- Resources that will help you to
Page 59 and 60: References For further readings 1.
Page 61 and 62: 28. Mulrow C, Cook D. Integrating h
Page 63 and 64: 58. Khoja TA. Glossary of Health Ca
Page 65 and 66: 85. Lorenz KA, Ryan GW, Morton CS.
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Evidence-Based Medicine

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