Institute:Office of National Coordinator (ONC) Workforce Training Curriculum
Component:The Culture of Health Care
Unit:Evidence-Based Practice
Lecture:Summarizing evidence
Putting evidence into practice
Slide content:Usual Meta-Analysis Summary Statistics Odds ratio (OR) Used for binary events, e.g., death, complication, recurrence Usually configured such that OR < 1 indicates treatment benefit If confidence interval (CI) does not cross OR = 1 line, then results are statistically significant Can calculate number needed to treat (NNT) from OR Weighted mean difference (WMD) Used for numeric events, e.g., measurements Usually configured such that WMD < 0 indicates treatment benefit If CI does not cross WMD = 0 line, then results are statistically significant 7
Slide notes:7 In discussing the meaning of summary statistics, the odds ratio is used for binary events. Many studies are reported in terms of how they reduce certain events that were trying to avoid, such as death, complications of a disease, the development of a myocardial infarction, high blood pressure, kidney disease, diabetes, the recurrence of a disease, or the re-emergence of cancer after initial treatment. Usually, the odds ratio statistic is configured when its less than one, which indicates theres a benefit for treatment. This is the approach, for example, that the Cochrane [ kock -rihn] Collaboration useswhich we talk about later in this lecture. When the odds ratio is less than one, then theres benefit for the treatment, and it turns out that when the confidence interval does not include the odds ratio equals 1 linewhen it does not cross over that lineour results are statistically significant. We can actually calculate, in a somewhat complicated formula, the number needed to treat from the odds ratios, so we can translate odds ratio findings into more meaningful information from a practical standpoint. The other summary statistic is weighted mean difference. This statistic is used for numeric events such as measurementsfor example, blood pressure value or blood sugar value. The weighted mean difference is usually configured such that a value less than zero indicates that theres a treatment benefit, and a value of greater than zero indicates that theres benefit for the control interventionjust as an odds ratio value of greater than one indicates that the control is of more benefit. Again, if the confidence interval crosses over the weighted mean difference equals zero line, or if it does not cross over that line, it means that the results are statistically significant.