The "number needed to treat" turns 20 -- and continues to be used and misused

McAlister, Finlay A.

doi:10.1503/cmaj.080484

Cited by 90 publications

(71 citation statements)

References 49 publications

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Section: Strengths and Limitationsmentioning

confidence: 97%

“…Whether the number needed to treat is appropriate for use in meta-analyses is controversial; however, we believe that the simplicity and transparency of this method outweigh its potential disadvantages. 21,60 Fifth, although we reported a wide range of clinically relevant outcomes as specified in our protocol, the definition for some (e.g., unstable angina) will have varied across trials.Sixth, in an attempt at unbiased identification of people at low cardiovascular risk, we based our inclusion criterion on the observed incidence of events among placebo recipients, anticipating that clinicians could apply our findings in practice by using their risk prediction instrument of choice to identify patients with an estimated 10-year risk of less than 20% for cardiovascular-related death or nonfatal myocardial infarction. Because risk prediction tools may overestimate true rates of events in contemporary practice, we re peated analyses after including only trials with an estimated 10-year risk of less than 20% based on mean participant characteristics and two widely used risk equations; 11,12 we reached similar conclusions.…”

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confidence: 97%

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Efficacy of statins for primary prevention in people at low cardiovascular risk: a meta-analysis

Tonelli

Lloyd²,

Clement³

et al. 2011

Canadian Medical Association Journal

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A lthough statins are known to improve survival and relevant clinical outcomes in high-risk populations, 1 evidence of their clinical benefit in lower risk populations is more equivocal. Initially, low-risk populations were defined by the absence of known coronary artery disease (and their treatment was termed "primary prevention"). However, it was subsequently recognized that these populations included both patients at very high risk of coronary artery disease (e.g., those with severe peripheral vascular disease) and those at very low risk (e.g., those aged < 40 years who have no diabetes or hypertension and have lowdensity lipoprotein cholesterol level of less than 1.8 mmol/L). Accordingly, current guidelines for the use of statins are based on the projected risk of an atherosclerotic event rather than solely on the presence or absence of known coronary artery disease. 2,3 Results of the recent JUPITER study (Justification for the Use of Statins in Prevention: an Intervention Trial Evaluating Rosuvastatin) 4 have renewed enthusiasm for the use of statins in people without a history of coronary artery disease and have generated further controversy as to whether high-potency statins such as rosuva statin and atorvastatin lead to better clinical outcomes than low-potency statins such as prava statin, simvastatin, fluvastatin and lovastatin. We did a systematic review of randomized trials to assess the efficacy and harms of statins in people at low cardiovascular risk, including indirect comparisons of high-potency and low-potency statins. Research CMAJ Background: Statins were initially used to improve cardiovascular outcomes in people with established coronary artery disease, but recently their use has become more common in people at low cardiovascular risk. We did a systematic review of randomized trials to assess the efficacy and harms of statins in these individuals. Efficacy of statins for primary prevention in people at low cardiovascular risk: a meta-analysis Methods:We searched MEDLINE and EMBASE (to Jan. 28, 2011), registries of health technology assessments and clinical trials, and reference lists of relevant reviews. We included trials that randomly assigned participants at low cardiovascular risk to receive a statin versus a placebo or no statin. We defined low risk as an observed 10-year risk of less than 20% for cardiovascular-related death or nonfatal myocardial infarction, but we explored other definitions in sensitivity analyses. Results:We identified 29 eligible trials involving a total of 80 711 participants. All-cause mortality was significantly lower among patients receiving a statin than among controls (relative risk [RR] 0.90, 95% confidence interval [CI] 0.84-0.97) for trials with a 10-year risk of cardiovascular disease < 20% [primary analysis] and 0.83, 95% CI 0.73-0.94, for trials with 10-year risk < 10% [sensitivity analysis]). Patients in the statin group were also significantly less likely than controls to have nonfatal myocardial infarction (RR 0.64, 95% CI 0.49-0.84) and nonfatal ...

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Section: Strengths and Limitationsmentioning

confidence: 97%

mentioning

confidence: 97%

Efficacy of statins for primary prevention in people at low cardiovascular risk: a meta-analysis

Tonelli

Lloyd²,

Clement³

et al. 2011

Canadian Medical Association Journal

Self Cite

123

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“…NNT is defined as the number of patients you need to treat to prevent one bad outcome. 15 NNT allows the results of the study to be placed in a clinician friendly metric which can be evaluated easily. The lower the number is the more effective the treatment.…”

Section: Evaluation Of Hard Outcomementioning

confidence: 99%

How to Interpret the Results of a Randomized Controlled Trial

Turlik¹

2009

FAOJ

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The Foot and Ankle Online Journal 2 (4): 4This is the third in a series of articles explaining basic concepts of evidence-based medicine to podiatric physicians. This article will explain how to evaluate the results section of a randomized controlled trial. This will be illustrated using actual examples from the foot and ankle literature to include an article which was referenced in the first article of this series.

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“…We do not know. Dichotomized results, although allowing for the use of number needed to treat (NNT)-one of the best approaches to evaluate measures of effectiveness [14]-obviously oversimplify our research findings in this area, generating a 'strained' or forced measure of a somewhat complex behaviour. These mechanisms, derived from other areas, measure results obtained from a model that cannot be superimposed to prevention programme models.…”

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confidence: 99%

Commentary on Bodin & Strandberg (2011): Scepticism, publication bias and a grain of salt – do we already know how to evaluate prevention programmes?

Pechansky¹

2011

Addiction

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The "number needed to treat" turns 20 -- and continues to be used and misused

Cited by 90 publications

References 49 publications

Efficacy of statins for primary prevention in people at low cardiovascular risk: a meta-analysis

Efficacy of statins for primary prevention in people at low cardiovascular risk: a meta-analysis

How to Interpret the Results of a Randomized Controlled Trial

Commentary on Bodin & Strandberg (2011): Scepticism, publication bias and a grain of salt – do we already know how to evaluate prevention programmes?

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