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| Volume 10, Issue 4 |
February 2005 |
SUMMARY: The following 9 papers, provided free in full-text by the publishers (click on blue links), constitute a series that is written by Dr Patricia Greenhalgh, primarily for physicians. Some of the Summary Points have been adapted below for Personal Injury lawyers.
| Summary points
Not all medical articles are indexed on Medline, and many that are have been misclassified Searching by textword can supplement a search by MeSH headings To increase the sensitivity of a search, use the "explode" command and avoid using subheadings Scan titles on screen rather than relying on the software to find the most valid or relevant ones |
| Summary points
Many papers published in medical journals have potentially serious methodological flaws When deciding whether a paper is valid and relevant to your litigation, first establish what specific clinical question it addressed Questions to do with drug treatment or other medical interventions should be addressed by double blind, randomised controlled trials Questions about prognosis require longitudinal cohort studies, and those about causation require either cohort or case-control studies Case reports, though methodologically weak, can be produced rapidly and have a place in alerting medical practitioners to adverse drug reactions |
| Summary points
The first essential question to ask about the methods section of a published paper is: was the study original? The second is: whom is the study about? Thirdly, was the design of the study sensible? Fourthly, was systematic bias avoided or minimised? Finally, was the study large enough, and continued for long enough, to make the results credible? |
| Summary points
In assessing the choice of statistical tests in a paper, first consider whether groups were analysed for their comparability at baseline Does the test chosen reflect the type of data analysed (parametric or non-parametric, paired or unpaired)? Has a two tailed test been performed whenever the effect of an intervention could conceivably be a negative one? Have the data been analysed according to the original study protocol? If obscure tests have been used, do the authors justify their choice and provide a reference? |
| Summary points
An association between two variables is likely to be causal if it is strong, consistent, specific, plausible, follows a logical time sequence, and shows a dose-response gradient A P value of <0.05 means that this result would have arisen by chance on less than one occasion in 20 The confidence interval around a result in a clinical trial indicates the limits within which the "real" difference between the treatments is likely to lie, and hence the strength of the inference that can be drawn from the result A statistically significant result may not be clinically significant. The results of intervention trials should be expressed in terms of the likely benefit an individual could expect (for example, the absolute risk reduction) |
| Summary points
Pharmaceutical "reps" are now much more informative than they used to be, but they may show ignorance of basic epidemiology and clinical trial design The value of a drug should be expressed in terms of safety, tolerability, efficacy, and price The efficacy of a drug should ideally be measured in terms of clinical end points that are relevant to patients; if surrogate end points are used they should be valid Promotional literature of low scientific validity (such as uncontrolled before and after trials) should not be used as evidence |
| Summary points
New tests should be validated by comparison against an established gold standard in an appropriate spectrum of subjects Diagnostic tests are seldom 100% accurate (false positives and false negatives will occur) A test is valid if it detects most people with the target disorder (high sensitivity) and excludes most people without the disorder (high specificity), and if a positive test usually indicates that the disorder is present (high positive predictive value) The best measure of the usefulness of a test is probably the likelihood ratio—how much more likely a positive test is to be found in someone with, as opposed to without, the disorder |
| Summary points
An economic analysis should be based on a primary study or meta-analysis that is scientifically valid, reliable, and relevant When deciding whether an economic analysis has been done correctly, you should not simply check the arithmetic but consider whether all direct, indirect, and intangible costs and benefits have been included In the allocation of limited resources, the comparison of different health states is unavoidable, but instruments for measuring health related quality of life are not as objective as they seem |
| Summary points
A systematic review is an overview of primary studies that used explicit and reproducible methods A meta-analysis is a mathematical synthesis of the results of two or more primary studies that addressed the same hypothesis in the same way Although meta-analysis can increase the precision of a result, it is important to ensure that the methods used for the review were valid and reliable |
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