Evaluating new cardiovascular risk factors for risk stratification.

Department of Internal Medicine, Division of Cardiovascular Medicine, University of Michigan, Ann Arbor, MI, USA.
Journal of Clinical Hypertension (Impact Factor: 2.96). 07/2008; 10(6):485-8. DOI: 10.1111/j.1751-7176.2008.07814.x
Source: PubMed
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    ABSTRACT: Authors have proposed new methodology in recent years for evaluating the improvement in prediction performance gained by adding a new predictor, Y, to a risk model containing a set of baseline predictors, X, for a binary outcome D. We prove theoretically that null hypotheses concerning no improvement in performance are equivalent to the simple null hypothesis that Y is not a risk factor when controlling for X, H(0) : P(D = 1 | X,Y ) = P(D = 1 | X). Therefore, testing for improvement in prediction performance is redundant if Y has already been shown to be a risk factor. We also investigate properties of tests through simulation studies, focusing on the change in the area under the ROC curve (AUC). An unexpected finding is that standard testing procedures that do not adjust for variability in estimated regression coefficients are extremely conservative. This may explain why the AUC is widely considered insensitive to improvements in prediction performance and suggests that the problem of insensitivity has to do with use of invalid procedures for inference rather than with the measure itself. To avoid redundant testing and use of potentially problematic methods for inference, we recommend that hypothesis testing for no improvement be limited to evaluation of Y as a risk factor, for which methods are well developed and widely available. Analyses of measures of prediction performance should focus on estimation rather than on testing for no improvement in performance. Copyright © 2013 John Wiley & Sons, Ltd.
    Statistics in Medicine 04/2013; 32(9). DOI:10.1002/sim.5727 · 2.04 Impact Factor
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    ABSTRACT: Risk stratification is a mainstay of current cardiovascular care. Its practical relevance to therapeutic decision making depends, however, on the often unverified assumption that higher risk patients experience greater treatment benefit. The truth of this assumption depends, in turn, on the particular set of variables in the putative risk prediction model, the pathophysiology of the underlying disease, and the associated goal(s) of therapy. If the operative set of risk predictors is incomplete (ignoring variables affected by treatment) or inconsistent (including variables unaffected by treatment), this will influence the relation between pretreatment risk and post-treatment benefit in complex ways having material clinical consequences. In conclusion, the clinical appropriateness of risk stratification must not be assumed. Instead, risk stratification guidelines specific to a particular disease and a particular treatment should be founded on prospective empiric validation.
    The American journal of cardiology 12/2011; 109(6):919-23. DOI:10.1016/j.amjcard.2011.10.056 · 3.43 Impact Factor
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    ABSTRACT: Purpose: To review the clinical benefits of inhibiting the renin–angiotensin system (RAS) through blood pressure (BP)–lowering and BP-independent mechanisms and to identify the benefits and potential limitations of RAS-blocking agents in various patient populations.Data sources: PubMed search using the key terms renin-angiotensin system, angiotensin-converting enzyme inhibitors, angiotensin-receptor blockers, aliskiren, heart failure, diabetes, and nephropathy. Current published guidelines from the Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure, American Diabetes Association, and National Kidney Foundation were reviewed.Conclusion: Antihypertensive treatment with an agent that inhibits the RAS effectively lowers BP in a broad range of patients. Whether these agents improve clinical outcomes is the subject of ongoing investigation. Results of recent trials suggest that for patients with or at risk of high-risk conditions, such as heart failure or diabetes, risk reduction with RAS-blocking agents may be independent of BP reduction. Inhibition of the RAS may also reduce risk of renal impairment.Implications for practice: RAS-blocking agents are important in a variety of patient populations at high cardiovascular risk, but while angiotensin-converting enzyme inhibitors have proven benefits in some cases, angiotensin receptor blockers may be preferred in others. Direct renin inhibitors are currently being evaluated. The nurse practitioner should become familiar with the evidence for use of these agents to reduce risk and improve outcomes in specific populations.
    Journal of the American Academy of Nurse Practitioners 12/2008; 21(1):66 - 75. DOI:10.1111/j.1745-7599.2008.00374.x · 0.87 Impact Factor


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