Evaluation of the benefits and harms of aspirin for primary prevention of cardiovascular events a comparison of quantitative approaches

We based our main analyses for these two approaches on the treatment effects from a meta-analysis of large primary prevention trials, and the incidence rates from observational studies. We focused on observational studies that were most applicable to our target population--aged 50 to 84 years, livin...

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Bibliographic Details
Main Author: Puhan, Milo A.
Corporate Authors: United States Agency for Healthcare Research and Quality, Johns Hopkins University Evidence-based Practice Center
Format: eBook
Language:English
Published: Rockville (MD) Agency for Healthcare Research and Quality (US) 2014, [2014]
Series:Methods research report
Subjects:
Online Access:
Collection: National Center for Biotechnology Information - Collection details see MPG.ReNa
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100 1 |a Puhan, Milo A. 
245 0 0 |a Evaluation of the benefits and harms of aspirin for primary prevention of cardiovascular events  |h Elektronische Ressource  |b a comparison of quantitative approaches  |c Milo A. Puhan, Sonal Singh, Carlos O. Weiss, Ravi Varadhan, Ritu Sharma, Cynthia M Boyd 
260 |a Rockville (MD)  |b Agency for Healthcare Research and Quality (US)  |c 2014, [2014] 
300 |a 1 PDF file (ix, 30, 2 pages) 
505 0 |a Includes bibliographical references 
653 |a Primary Prevention / methods 
653 |a Cardiovascular Diseases / prevention & control 
653 |a Aspirin / therapeutic use 
710 2 |a United States  |b Agency for Healthcare Research and Quality 
710 2 |a Johns Hopkins University  |b Evidence-based Practice Center 
041 0 7 |a eng  |2 ISO 639-2 
989 |b NCBI  |a National Center for Biotechnology Information 
490 0 |a Methods research report 
500 |a Title from PDF title page. - "November 2013. Updated February 2014." 
856 4 0 |u https://www.ncbi.nlm.nih.gov/books/NBK179079  |3 Volltext  |n NLM Bookshelf Books  |3 Volltext 
082 0 |a 610 
520 |a We based our main analyses for these two approaches on the treatment effects from a meta-analysis of large primary prevention trials, and the incidence rates from observational studies. We focused on observational studies that were most applicable to our target population--aged 50 to 84 years, living in the United States without evidence of cardiovascular disease or stroke. We obtained relative weights denoting the relative importance of different outcomes (required by the Gail/NCI approach) from literature sources. These sources weighted major stroke nearly twice as much as MI and nearly eight times as much as major GI bleeds. RESULTS: The NNT and NNH for aspirin declined with increasing age because of the increase in baseline incidence rates for all outcomes across age categories as obtained from observational studies.  
520 |a When we weighted outcomes equally in a sensitivity analysis, the harm from aspirin was much greater compared with the main analysis because of greater relative weight for GI bleeds. When we weighted stroke as a very important outcome (weight of 1), MI as an important outcome (weight of 0.5), and GI bleed as an unimportant outcome (weight of 0), aspirin was associated with net benefit for all sex and age categories. When comparing the two approaches in terms of estimates for a single outcome, we found comparable results for the number of people who would have a benefit or harm from treatment as long as the baseline incidence rates and the competing risk (all-cause mortality) were small. When the impact of the competing risk was larger, we found substantial differences between the NNT and NNH and Gail/NCI approaches, even though the baseline incidence rates and treatment effects used were identical.  
520 |a BACKGROUND: Prior work has described various quantitative approaches to the assessment of benefits and harms of medical interventions. Researchers rarely use these approaches in the context of a systematic review. OBJECTIVE: Our objectives were to illustrate two quantitative approaches to assessing benefits and harms in the context of a systematic review, and to determine the methodological challenges of applying these approaches in a systematic review. METHODS: We compared the number-needed-to-treat (NNT) and number-needed-to-harm (NNH) approach and the Gail/National Cancer Institute (NCI) approach for assessing the benefits (prevention of myocardial infarction [MI] and ischemic stroke) and harms (excess of hemorrhagic stroke and major gastrointestinal [GI] bleeds) of aspirin for primary prevention of cardiovascular events.  
520 |a For example, in men aged 45-54, the NNT was 1,786 person-years of treatment to prevent one MI, and the NNH was 202 person-years of treatment to induce one major GI bleed (which corresponds to 5.6 MI prevented and 49.5 GI bleeds induced if 1,000 people are treated with aspirin for 10 years, compared with no aspirin use). For men aged 75-84, the NNT was 511 to prevent one MI and the NNH was 34 to induce one major GI bleed. A sensitivity analysis that considered different baseline incidence rates from randomized trials showed a much higher NNH for GI bleeds because the baseline incidence rate of that outcome was 10-15 times lower than in observational studies. When we used relative weights, the Gail/NCI approach showed that aspirin caused more harm than benefit in all age categories of men and women despite the low weight assigned to GI bleeds.  
520 |a CONCLUSION: The assessment of benefits and harms requires careful selection and integration of data from disparate sources, including baseline risks of events without treatment, the effects of treatments on various outcomes, and relative weights of these outcomes. We have illustrated that quantitative approaches are feasible in a specific decisionmaking context--using data from a systematic review of aspirin for primary prevention. Quantitative approaches can yield different results even if input data for baseline risks and treatment effects are identical. Quantitative approaches can be particularly valuable in demonstrating how the expected balance of benefits and harms depends on assumptions about the relative weights of different outcomes