Common pitfalls in statistical analysis: Absolute risk reduction, relative risk reduction, and number needed to treat

Tips for learners of evidence-based medicine: 1. Relative risk reduction, absolute risk reduction and number needed to treat.

Physicians, patients and policy-makers are influenced not only by the results of studies but also by how authors present the results. Depending on which measures of effect authors choose, the impact of an intervention may appear very large or quite small, even though the underlying data are the same. In this article we present 3 measures of effect — relative risk reduction, absolute risk reduct...

Measuring the Size of a Treatment Effect: Relative Risk Reduction, Absolute Risk Reduction, and Number Needed to Treat

Hussein Hollands, MD, MS (epid) Peter J. Kertes, MD, CM, FRCS(C) The purpose of this review article is to outline a few concepts that are useful for interpreting the results of a randomized clinical trial (RCT). Specifically, we will focus on measures of the size of a treatment effect— relative risk ratio (RRR), absolute risk ratio, and number needed to treat (NNT). These concepts are important...

Reporting number needed to treat and absolute risk reduction in randomized controlled trials.

CONTEXT Ongoing efforts to improve the quality of reporting for randomized controlled trials (RCTs) include the Consolidated Standards of Reporting Trials (CONSORT) statement. We examined the frequency of explicit reporting of the number needed to treat (NNT) and the absolute risk reduction (ARR) in RCTs. METHODS Five frequently cited journals were investigated: Annals of Internal Medicine, B...

Relative Risk, Odds Ratio, Attributable Risk and Number Needed to Treat

The research may or may not be epidemiological but there is a high likelihood that it would use the epidemiological indices discussed in this note. Rate, risk, hazard, incidence, and prevalence are everyday indices of disease occurrence that are used in a large number of research endeavours. Although these indices apparently look simple but many researchers are not fully comfortable in their us...

Number Needed to Treat