It is important that only studies matching the inclusion criteria are included in the systematic review, so that the systematic review answers a specific clinical question. Prospective criteria for study inclusion and exclusion should be explicitly SCH727965 mouse stated in the review to minimize selectivity by authors. These criteria are a requirement before commencing Cochrane reviews, when a study protocol is developed, peer reviewed and published before initiating the review. The decision regarding which studies to include in a systematic review may have an important effect on a conclusion, say regarding the overall utility

of a healthcare intervention.13 Therefore, study inclusion assessment should be completed independently by at least two authors and generally is arbitrated by a third. Readers of systematic reviews can look for a flow chart (usually presented as a Fig. 1) describing the details of studies identified, studies excluded, reasons for exclusion and numbers of studies included in the final review. If the outcome of interest is dichotomous (the outcome

is one of two possibilities – example, death or survival) the treatment effect is calculated for each trial as a risk ratio, an odds ratio or a risk difference together with the 95% confidence interval (95% CI; the range Obeticholic Acid research buy within which we are 95% confident that the effect calculated is likely to exist). While full discussion of all methods Methane monooxygenase is beyond the scope of this review, dichotomous outcomes are frequently evaluated as a relative risk (RR), which deserves a brief explanation. A RR divides the event rate in the intervention group (number of events divided by the total number of individuals randomized in that group) by the event rate in the comparison group. For example, if 20 of 100 patients in the active intervention group who are randomized to

erythropoietin to normalize haemoglobin levels experienced an event and 10 of 100 patients in the control group (those randomized to a lower haemoglobin target), experienced the event, then the RR is 2 (20/100 divided by 10/100), indicating that the intervention is twice more likely than the comparison treatment to result in the outcome. Interpretation of this risk for the specific patient is possible when the actual risk of the outcome for that patient without treatment is known (e.g. when RR = 2, a doubling of risk from 2% to 4% is quite different from the doubling of risk from 10% to 20% in the present example). If the outcome of interest is a continuous variable (an example is systolic blood pressure, mmHg), then the effect size of the intervention is summarized as a mean difference (MD; and its 95% CI). The MD for the outcome in each trial is the amount by which an intervention changes the outcome on average compared with the control.