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Validation of the Pooled Cohort 10-year Atherosclerotic Cardiovascular Disease Risk Equations

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Title: Validation of the Pooled Cohort 10-year Atherosclerotic Cardiovascular Disease Risk Equations


1
Validation of the Pooled Cohort 10-year
Atherosclerotic Cardiovascular Disease Risk
Equations
  • Paul Muntner, Lisandro D Colantonio, Mary
    Cushman, David C Goff Jr., George Howard,
    Virginia J Howard, Brett Kissela, Emily B
    Levitan,
  • Donald M. Lloyd-Jones, Monika M Safford
  • University of Alabama at Birmingham, University
    of Vermont, University of Colorado, University of
    Cincinnati, Northwestern University.

On behalf of REGARDS and REGARDS-MI This study
was supported by U01 NS041588 (NINDS) and R01
HL080477, K24 HL111154 (NHLBI)
2
Disclosures
  • Drs. Muntner, Howard, Levitan, and Safford have
    received grant funding from Amgen Inc. for work
    unrelated to this presentation.
  • Dr. Muntner has served on an advisory board for
    Amgen Inc.
  • Drs. Cushman and Safford have served as
    consultants for DiaDexus.

3
Background
  • In 2013, the American College of Cardiology /
    American Heart Association (ACC/AHA) published a
    guideline for the estimation of atherosclerotic
    cardiovascular disease (ASCVD) risk.
  • This guideline included the development of the
    Pooled Cohort risk equations for estimating
    10-year risk for incident ASCVD.
  • These equations can be used to guide the decision
    to initiate statins for people 40-79 years
    without ASCVD or diabetes and with LDL-C of 70 to
    189 mg/dL clinically relevant population.
  • Consideration of statin treatment is recommended
    for adults with a 10-year ASCVD risk 7.5

Goff, J Am Coll Cardiol 2013 Stone, J Am Coll
Cardiol 2013
4
Background
  • The Pooled Cohort risk equations were developed
    using data from several studies conducted before
    2000. Marked declines in ASCVD incidence have
    occurred over the past 2 decades.
  • These equations were reported to over-estimate
    risk in analyses of the Womens Health Study,
    Womens Health Initiative and the Physicians
    Health Study.
  • Prior analyses
  • Did not focus on the population for whom the
    equations may inform a discussion to initiate
    statins.
  • Did not have surveillance components

Rosamond, Circulation 2012 Kleindorfer, Stroke
2010 Ridker, Lancet 2013
5
Objective
  • To evaluate the validity of the Pooled Cohort
    risk equations in a contemporary US population
    for whom the equations are intended to inform
    discussions about initiating statins.
  • We assessed
  • Calibration
  • Do the Pooled Cohort risk equations accurately
    estimate the observed absolute risk level?
  • Discrimination
  • Are individuals with higher predicted risk more
    likely to have events?

6
Methods
  • We used data from the REasons for Geographic And
    Racial Differences in Stroke (REGARDS) study
  • Population-based cohort of 30,239 blacks and
    whites
  • 45 years of age residing in 48 contiguous US
    states and Washington, DC
  • Enrolled between January 2003 and October 2007.
  • All participants provided written informed
    consent.
  • Primary analyses focused on the clinically
    relevant population
  • Those for whom 10-year ASCVD risk can be used to
    guide decision-making
  • We excluded participants taking statins, with
    ASCVD or diabetes, an LDL-C 190 mg/dL or lt 70
    mg/dL, and 80 years of age or older.

Howard, Neuroepidemiology 2005 Safford, JAMA 2012
7
Methods Statistical Methods
  • We calculated 10-year ASCVD predicted risk at
    baseline using the race-sex specific Pooled
    Cohort risk equations.
  • Participants were stratified by decile of 10-year
    predicted risk.
  • Calibration was analyzed by comparing observed
    and predicted number of ASCVD events at 5 years
  • We used a modified Hosmer-Lemeshow test.
  • A chi-square gt20 or p-value lt0.05 indicates poor
    calibration.
  • Discrimination was analyzed
  • We used the C-index.
  • A C-index between 0.70 and 0.80 is good and 0.80
    is excellent.

8
Pooled Cohort risk equations
  •  
  • Individual score calculation is based on
  • Age
  • Total cholesterol
  • HDL cholesterol
  • Systolic blood pressure
  • Use of antihypertensive medication
  • Current smoker
  • Diabetes

  S0(t) at 5 years S0(t) at 10 years Mean score
Black women 0.98194 0.9533 86.61
White women 0.98898 0.9665 -29.18
Black men 0.95726 0.8954 19.54
White men 0.96254 0.9144 61.18
HDL high-density lipoprotein
Personal communication (Coady, S).
Goff, et al. Circulation 2013
9
Methods Two sets of outcomes were evaluated
  • ASCVD outcomes Non-fatal myocardial infarction,
    CHD death or non-fatal or fatal stroke.
  • Adjudicated outcomes - Participant were contacted
    every 6 months and self-reported events were
    adjudicated.
  • Surveillance outcomes - Medicare claims were
    searched for myocardial infarction and stroke
    events
  • Limited to participants 65 years of age and
    older.
  • Medicare Part A coverage required
  • Outcomes identified using validated algorithms.
  • Outcomes were available through December 31,
    2010.

Kiyota, Am Heart J 2004, Tirschwell, Stroke 2002
10
Flowchart of participants included in the analysis
Defined by use of digoxin. Or non-HDL-C of
100 - 219 mg/dL for those without a valid LDL-C
measurement.
11
Baseline characteristics of participants
  Clinically relevant population (n10,997) Medicare-linked population (n3,333)
Age (years), mean (SD) 62 (8) 71 (4)
Blacks, n () 4,132 (38) 1,095 (33)
Men, n () 4,480 (41) 1,476 (44)
Current smoking, n () 1,626 (15) 348 (10)
SBP (mmHg), mean (SD) 124.8 (16) 128.3 (16)
Antihypertensive med, n () 4,134 (38) 1,491 (45)
Total-C (mg/dL), mean (SD) 203 (31) 202 (31)
HDL-C (mg/dL), mean (SD) 54 (17) 55 (17)
The clinically relevant population included those not taking statins, without ASCVD or diabetes, and with LDL-C 70 to 189 mg/dL. SD standard deviation SBP systolic blood pressure HDL high density lipoprotein. The clinically relevant population included those not taking statins, without ASCVD or diabetes, and with LDL-C 70 to 189 mg/dL. SD standard deviation SBP systolic blood pressure HDL high density lipoprotein. The clinically relevant population included those not taking statins, without ASCVD or diabetes, and with LDL-C 70 to 189 mg/dL. SD standard deviation SBP systolic blood pressure HDL high density lipoprotein.
12
Calibration Clinically relevant population
13
Results Calibration and discrimination in the
clinically relevant population
  Events / person-years Events in 5-years Events in 5-years 5-year incidence rate 5-year incidence rate Discrimination
  Events / person-years Observed Predicted Observed (95 CI) Predicted C-index (95 CI)
10-year predicted risk Clinically relevant population Clinically relevant population Clinically relevant population Clinically relevant population Clinically relevant population 0.72 (0.70-0.75)
lt5 28 / 14,816 32 33 1.9 (1.3-2.7) 1.9
5 to lt7.5 32 / 6,866 38 38 4.8 (3.4-6.7) 4.8
7.5 to lt10 34 / 5,853 41 46 6.1 (4.4-8.6) 6.9
10 244 / 19,946 278 350 12.0 (10.6-13.6) 15.1
REGARDS participants without diabetes, with LDL-C 70 to 189 mg/dL who were not taking statins are included in this table. 95 CI 95 confidence interval. HDL-C high density lipoprotein cholesterol KM Kaplan-Meier LDL-C low density lipoprotein cholesterol REGARDS REasons for Geographic And Racial Differences in Stroke. Per 1,000 person-years. Kaplan-Meier adjusted. Or non-HDL-C of 100 - 219 mg/dL for those without a valid LDL-C measurement. REGARDS participants without diabetes, with LDL-C 70 to 189 mg/dL who were not taking statins are included in this table. 95 CI 95 confidence interval. HDL-C high density lipoprotein cholesterol KM Kaplan-Meier LDL-C low density lipoprotein cholesterol REGARDS REasons for Geographic And Racial Differences in Stroke. Per 1,000 person-years. Kaplan-Meier adjusted. Or non-HDL-C of 100 - 219 mg/dL for those without a valid LDL-C measurement. REGARDS participants without diabetes, with LDL-C 70 to 189 mg/dL who were not taking statins are included in this table. 95 CI 95 confidence interval. HDL-C high density lipoprotein cholesterol KM Kaplan-Meier LDL-C low density lipoprotein cholesterol REGARDS REasons for Geographic And Racial Differences in Stroke. Per 1,000 person-years. Kaplan-Meier adjusted. Or non-HDL-C of 100 - 219 mg/dL for those without a valid LDL-C measurement. REGARDS participants without diabetes, with LDL-C 70 to 189 mg/dL who were not taking statins are included in this table. 95 CI 95 confidence interval. HDL-C high density lipoprotein cholesterol KM Kaplan-Meier LDL-C low density lipoprotein cholesterol REGARDS REasons for Geographic And Racial Differences in Stroke. Per 1,000 person-years. Kaplan-Meier adjusted. Or non-HDL-C of 100 - 219 mg/dL for those without a valid LDL-C measurement. REGARDS participants without diabetes, with LDL-C 70 to 189 mg/dL who were not taking statins are included in this table. 95 CI 95 confidence interval. HDL-C high density lipoprotein cholesterol KM Kaplan-Meier LDL-C low density lipoprotein cholesterol REGARDS REasons for Geographic And Racial Differences in Stroke. Per 1,000 person-years. Kaplan-Meier adjusted. Or non-HDL-C of 100 - 219 mg/dL for those without a valid LDL-C measurement. REGARDS participants without diabetes, with LDL-C 70 to 189 mg/dL who were not taking statins are included in this table. 95 CI 95 confidence interval. HDL-C high density lipoprotein cholesterol KM Kaplan-Meier LDL-C low density lipoprotein cholesterol REGARDS REasons for Geographic And Racial Differences in Stroke. Per 1,000 person-years. Kaplan-Meier adjusted. Or non-HDL-C of 100 - 219 mg/dL for those without a valid LDL-C measurement. REGARDS participants without diabetes, with LDL-C 70 to 189 mg/dL who were not taking statins are included in this table. 95 CI 95 confidence interval. HDL-C high density lipoprotein cholesterol KM Kaplan-Meier LDL-C low density lipoprotein cholesterol REGARDS REasons for Geographic And Racial Differences in Stroke. Per 1,000 person-years. Kaplan-Meier adjusted. Or non-HDL-C of 100 - 219 mg/dL for those without a valid LDL-C measurement.
14
Calibration REGARDS Medicare-linked population
15
Results - Calibration and discrimination for
REGARDS Medicare-linked population
  Events / person-years Events in 5-years Events in 5-years 5-year incidence rate 5-year incidence rate Discrimination
  Events / person-years Observed Predicted Observed (95 CI) Predicted C-index (95 CI)
10-year predicted risk Medicare linked participants Medicare linked participants Medicare linked participants Medicare linked participants Medicare linked participants 0.67 (0.64-0.71)
5 to lt7.5 (Suppressed) 9 7 5.3 (2.8-10.1) 4.0
7.5 to lt10 (Suppressed) 15 12 7.9 (4.6-13.5) 6.4
10 212 / 11,754 226 215 17.4 (15.3-19.8) 16.4
REGARDS participants without diabetes, with LDL-C 70 to 189 mg/dL who were not taking statins are included in this table. Suppressed Medicare data are not presented in these cells due to a small sample size. 95 CI 95 confidence interval. HDL-C high density lipoprotein cholesterol KM Kaplan-Meier LDL-C low density lipoprotein cholesterol REGARDS REasons for Geographic And Racial Differences in Stroke. Per 1,000 person-years. Kaplan-Meier adjusted. Or non-HDL-C of 100 - 219 mg/dL for those without a valid LDL-C measurement. REGARDS participants without diabetes, with LDL-C 70 to 189 mg/dL who were not taking statins are included in this table. Suppressed Medicare data are not presented in these cells due to a small sample size. 95 CI 95 confidence interval. HDL-C high density lipoprotein cholesterol KM Kaplan-Meier LDL-C low density lipoprotein cholesterol REGARDS REasons for Geographic And Racial Differences in Stroke. Per 1,000 person-years. Kaplan-Meier adjusted. Or non-HDL-C of 100 - 219 mg/dL for those without a valid LDL-C measurement. REGARDS participants without diabetes, with LDL-C 70 to 189 mg/dL who were not taking statins are included in this table. Suppressed Medicare data are not presented in these cells due to a small sample size. 95 CI 95 confidence interval. HDL-C high density lipoprotein cholesterol KM Kaplan-Meier LDL-C low density lipoprotein cholesterol REGARDS REasons for Geographic And Racial Differences in Stroke. Per 1,000 person-years. Kaplan-Meier adjusted. Or non-HDL-C of 100 - 219 mg/dL for those without a valid LDL-C measurement. REGARDS participants without diabetes, with LDL-C 70 to 189 mg/dL who were not taking statins are included in this table. Suppressed Medicare data are not presented in these cells due to a small sample size. 95 CI 95 confidence interval. HDL-C high density lipoprotein cholesterol KM Kaplan-Meier LDL-C low density lipoprotein cholesterol REGARDS REasons for Geographic And Racial Differences in Stroke. Per 1,000 person-years. Kaplan-Meier adjusted. Or non-HDL-C of 100 - 219 mg/dL for those without a valid LDL-C measurement. REGARDS participants without diabetes, with LDL-C 70 to 189 mg/dL who were not taking statins are included in this table. Suppressed Medicare data are not presented in these cells due to a small sample size. 95 CI 95 confidence interval. HDL-C high density lipoprotein cholesterol KM Kaplan-Meier LDL-C low density lipoprotein cholesterol REGARDS REasons for Geographic And Racial Differences in Stroke. Per 1,000 person-years. Kaplan-Meier adjusted. Or non-HDL-C of 100 - 219 mg/dL for those without a valid LDL-C measurement. REGARDS participants without diabetes, with LDL-C 70 to 189 mg/dL who were not taking statins are included in this table. Suppressed Medicare data are not presented in these cells due to a small sample size. 95 CI 95 confidence interval. HDL-C high density lipoprotein cholesterol KM Kaplan-Meier LDL-C low density lipoprotein cholesterol REGARDS REasons for Geographic And Racial Differences in Stroke. Per 1,000 person-years. Kaplan-Meier adjusted. Or non-HDL-C of 100 - 219 mg/dL for those without a valid LDL-C measurement. REGARDS participants without diabetes, with LDL-C 70 to 189 mg/dL who were not taking statins are included in this table. Suppressed Medicare data are not presented in these cells due to a small sample size. 95 CI 95 confidence interval. HDL-C high density lipoprotein cholesterol KM Kaplan-Meier LDL-C low density lipoprotein cholesterol REGARDS REasons for Geographic And Racial Differences in Stroke. Per 1,000 person-years. Kaplan-Meier adjusted. Or non-HDL-C of 100 - 219 mg/dL for those without a valid LDL-C measurement.
16
Conclusion
  • In this cohort of US adults for whom statin
    initiation may be considered based on 10-year
    predicted ASCVD risk
  • Observed and predicted 5-year ASCVD risks were
    similar indicating that these risk equations were
    well calibrated.
  • Discrimination was moderate/good.
  • Previous results of over-estimation of ASCVD risk
    are likely due to incomplete capture of ASCVD
    events and inclusion of participants taking
    statins.
  • The current study supports the validity of the
    Pooled Cohort risk equations to inform clinical
    management decisions.

17
P Muntner and coauthors Validation of the
Atherosclerotic Cardiovascular Disease Pooled
Cohort Risk Equations Published online March 29,
2014
Available at www.jama.com and also at
mobile.jamanetwork.com
jamanetwork.com
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