(Circulation. 2007;115:928-935.)
© 2007 American Heart Association, Inc.
Special Report |
From the Division of Preventive Medicine, Department of Medicine, Brigham and Womens Hospital, Harvard Medical School, Boston, Mass, and the Department of Epidemiology, Harvard School of Public Health, Boston, Mass.
Correspondence to Dr Nancy R. Cook, Division of Preventive Medicine, Brigham and Womens Hospital, 900 Commonwealth Ave East, Boston, MA 02215. E-mail ncook{at}rics.bwh.harvard.edu
| Abstract |
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Key Words: cardiovascular diseases epidemiology follow-up studies prevention risk factors statistics risk
| Introduction |
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The accuracy of models can be assessed in several ways. Two major components are calibration and discrimination.2 Calibration is a measure of how well predicted probabilities agree with actual observed risk. When the average predicted risk within subgroups of a prospective cohort, for example, matches the proportion that actually develops disease, we say a model is well calibrated. The Hosmer-Lemeshow statistic3 compares these proportions directly and is a popular, though imperfect,4 means to assess model calibration.
Discrimination is a measure of how well the model can separate those who do and do not have the disease of interest. If the predicted values for cases are all higher than for non-cases, we say the model can discriminate perfectly, even if the predicted risk does not match the proportion with disease. Discrimination is of most interest when classification into groups with or without prevalent disease is the goal, such as in diagnostic testing.5 Discrimination is most often measured by the area under the receiver operating characteristic (ROC) curve, or c statistic, as described below.
In the diagnostic setting the outcome is already determined but unknown to the investigator, and the estimated classification can often be compared with a more expensive or invasive gold standard. In prognostic modeling or risk stratification, however, the outcome has not yet developed at the time that predictors are assessed. Future disease status remains to be determined by stochastic process, and can only be estimated as a probability or risk.6 Measures of discrimination are nonetheless commonly emphasized in such settings, which ignores the random nature of the outcome. Calibration, as well as discrimination, is important in accurate risk prediction. More global measures of fit that combine calibration and discrimination exist, such as likelihood statistics, R2, and the Brier score.2,7 The performance of risk prediction models in the cardiovascular literature, however, is often judged solely on the basis of the c statistic,814 despite the existence of large prospective cohort studies from which risk can be estimated directly.
| The ROC Curve and the c Statistic |
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The ROC curve is a plot of sensitivity versus 1specificity (often called the false-positive rate) that offers a summary of sensitivity and specificity across a range of cut points for a continuous predictor. The area under the curve, or cstatistic, ranges from 0.5 (no discrimination) to a theoretical maximum of 1. Perfect discrimination corresponds to a cstatistic of 1 and is achieved if the scores for all the cases are higher than those for all the non-cases, with no overlap. The cstatistic is equivalent to the probability that the measure or predicted risk is higher for a case than for a noncase.15 Note that the cstatistic is not the probability that individuals are classified correctly or that a person with a high test score will eventually become a case. The latter is closer in meaning to the predictive value, or the probability of disease given the test result.
The cstatistic also describes how well models can rank order cases and noncases, but is not a function of the actual predicted probabilities. For example, a model that assigns all cases a value of 0.52 and all noncases a value of 0.51 would have perfect discrimination, although the probabilities it assigns may not be helpful. The actual predicted probabilities do matter, however, in clinical risk prediction models such as those commonly used for the assessment of global cardiovascular risk.
In a prospective cohort that is considered generally low-risk, such as many population-based cohorts, there may be a small proportion of individuals who are at high risk, with a preponderance of those at low or very low risk. Rank-based measures such as the cstatistic do not take this distribution into account. Differences between 2 individuals who are at very low risk (eg, 1.0% versus 1.1%) have the same impact on the cstatistic as 2 individuals who are at moderate versus high risk (eg, 5% versus 20%) if their differences in rank are the same. Clinically, however, it may be more important to separate the latter 2 individuals, particularly if treatment decisions are based on predicted probabilities, such as those used by the Adult Treatment Panel III.1
| cStatistics and Model Selection |
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2 statistics indicate that, after age, systolic blood pressure (SBP) is the strongest predictor of risk, followed by smoking and lipids. To directly compare the magnitude of effects in this population, the rate (hazard) ratios per 2 SD units are shown, roughly comparable to a comparison of risks for extreme tertiles. The rate ratios lie in the same order as the likelihood ratio statistics for the continuous variables.
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The cstatistic in the model that included only age is 0.70 (Table 1), based on the generalized c index for censored data. This means that the probability is 70% that a case is older than a noncase. When SBP is added to the models, the cstatistic improves to 0.74, which means that the probability that the predicted risk is higher in cases than noncases is 74%. Although the likelihood ratio statistics and the rate ratios suggest that SBP is the strongest predictor after age, the cstatistic is 73% to 74% for models with SBP, smoking, and high-density lipoprotein cholesterol (HDL-C), and is unable to distinguish between these 3 factors. The cstatistic is only 0.71 for the model that includes age and low-density lipoprotein cholesterol (LDL-C). This failure to improve the cstatistic would suggest that LDL-C is not predictive of CVD, even though it is highly statistically significant in these data, the effect size is moderate, and we know from many studies and trials that LDL-C is an important modifiable risk factor for CVD. An example of improved predictive accuracy despite little change in the cstatistic is given below.
In a similar manner, with age, SBP, and smoking together in the model for future CVD risk, the cstatistic was 0.76, and improved only slightly to 0.77 when any of the lipids were added individually (Table 1, middle). Despite this, the likelihood statistics and the rate ratios indicate that HDL-C is a strong cardiovascular risk predictor, followed by total and LDL cholesterol. Finally, when each variable was in turn removed from the full model (Table 1, bottom), the cstatistic dropped from 0.78 to only 0.77 or 0.76 for all variables except age. Thus, in this example, the likelihood-based measures of model fit were able to distinguish the importance of several established risk factors, whereas the cstatistic could not. Indeed, if improvement in the cstatistic was used as the criterion for model inclusion, then neither LDL-C, HDL-C, nor total cholesterol would have been included in risk models after accounting for age, blood pressure, and smoking. In an example from the Framingham Heart Study, family history of premature atherosclerosis was found to be an independent predictor of cardiovascular events, with a relative risk of 2.0 for men and 1.7 for women.21 However, the cstatistic increased only from 0.80 to 0.81 in men and 0.81 to 0.82 in women, which may inappropriately limit enthusiasm for this variable.
In these examples, sole reliance on the cstatistic would seem ill-advised because discrimination is only one aspect of model performance. Likelihood-based measures, such as the likelihood ratio statistic or the Bayes information criterion, which adjusts for the number of variables in the model, are alternatives that are more sensitive and more global measures of model fit.2 Use of these criteria would have selected age, SBP, smoking, total cholesterol, and HDL-C from the variables considered in Table 1, and reached a final model similar to that developed from the Framingham data.1,22
| Odds Ratios and Predictive Values |
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Consider, for example, a novel biomarker that has a relative risk of 3.0, but leads to little or no improvement in the cstatistic given traditional risk factors. For some patients, a high level of the biomarker would shift estimated 10-year risk from 1% to only 3%, a clinically unimportant difference. For others, the same high biomarker level could alter the estimated 10-year risk of a cardiovascular event from 8% to 24%, and lead to different treatment recommendations under current Adult Treatment Panel III guidelines. Thus, for risk prediction, the actual or absolute predicted risk, which is not captured by the cstatistic, is of primary clinical interest.
Figure 1 shows the distribution of a hypothetical normally distributed risk factor X among cases and controls. Among controls the mean is 0, with a SD of 0.5. Suppose that the OR per 2 SD units equals 3.0, which corresponds to a cstatistic of 0.65. Despite this moderately large OR, there is a great deal of overlap between the distributions for cases and noncases. This extent of overlap often occurs in practice, as evidenced by the distributions of total cholesterol among cases and noncases of coronary heart disease in the Framingham study.24 Thus, total cholesterol by itself would be considered a poor classifier for cardiovascular risk, even though it is known to be a pathophysiological determinant of disease.
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The OR does, however, relate to the predictive value, or the probability of disease given a positive test, or a value above a threshold. This is a direct function of the OR. Figure 1 also plots the probability of disease given the value of risk factor X in a population with an overall disease probability of 10%. Despite the overlap in the distributions, the predicted probabilities range from <5% to >25%, a difference that may be clinically important. Although the actual numbers may depend on overall disease incidence, the revised risk could cross risk strata in treatment guidelines and lead to different treatment decisions.
SBP provides a more concrete example. Among men in National Health and Nutrition Evaluation Study II data, the estimated mean SBP is 129 mm Hg (SD 17.7).25 An OR of 3.0 would correspond to a mean of 139 mm Hg among cases, or a difference of 10 mm Hg between cases and noncases (Table 2). Corresponding differences in other measures would be 6 mm Hg for diastolic blood pressure, 24 mg/dL for total cholesterol, 21 mg/dL for LDL-C, and 8 mg/dL for HDL-C,25,26 all of which would appear to be clinically important differences. None of these by itself, however, would lead to substantial improvement in the area under the ROC curve.
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Pepe23 suggests that an OR of about 16, which corresponds to a cstatistic of about 0.84, may be needed to achieve reasonable discrimination, or classification into cases and noncases. As shown in Table 2, this would require much larger differences in means between cases and noncases, as large as 24 mm Hg in SBP and 62 mg/dL for total cholesterol. It is unlikely that a single marker could achieve such levels of separation and discrimination. It is, however, possible for a score composed of several of these predictors together to achieve this target. Thus, the Framingham score, which includes several traditional risk factors, has been shown to discriminate reasonably well.22
Thus, if a relative risk >3.0 were required as a strict criterion for inclusion of each additional biomarker in risk prediction, then, except for age, few of the components of the Framingham risk score would be eligible for inclusion. In the Framingham model,22 none of the risk factors besides age, which include blood pressure, smoking, or lipids, individually achieves a rate ratio higher than 1.9 for men or 2.2 for women. Although the Framingham score as a whole, including age, increased the cstatistic from 0.5 (ie, from chance alone with no predictors used) to 0.74 in men and 0.77 in women, the individual clinical risk factors could not do so based on their conditional relative risks. Use of an improvement in the ROC curve for each individual biomarker as a criterion, then, would eliminate most risk factors currently in use for cardiovascular risk prediction, which would include lipids, blood pressure, and smoking.
| Predictive Values and Calibration |
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In a population similar to the Womens Health Study cohort, with a low average 10-year risk of 2.5% and a 99th percentile of 23%, the maximum cstatistic is 0.89. In a population with a higher overall risk of 10% and a 99th percentile of 40%, closer to that for coronary heart disease (inclusive of angina) in the Framingham cohort,22 the maximum cstatistic is 0.76. Both perfect calibration and perfect discrimination could be achieved only if the true risk as well as the estimated risk were either 0 or 1, similar to the U-shaped distribution in Figure 2 (right). This may be true in the diagnostic setting where the outcome is determined, and the individual truly does or does not have disease. In the prediction of 10-year CVD risk in population-based cohorts, however, the maximum cstatistic for perfectly calibrated models appears to be
0.75 to 0.90.
A related way to compare models is to examine curves of predicted values or estimated risk (as opposed to true risk, which is unknown).29 In theory, a stronger model should lead to a wider spread of predicted values and, consequently, stronger discrimination. A plot of the predicted risk versus the risk percentile has been used to compare models.29,30 Such distributions may, however, also be insensitive in distinguishing between models. An example is shown in Figure 3, which plots the predicted risk from models in the Womens Health Study that include age, smoking, total and HDL cholesterol, but with and without SBP in the model. Transposition of the x and y axes yields a plot of the cumulative probability distribution functions. As shown, there is little difference in these curves even though SBP is the strongest risk predictor after age. The populations in the plot also do not tell us whether 1 model estimates risk more accurately or how the predicted risks differ for individuals with the 2 models. A look at conditional or joint distributions of predicted risk, as described below, may give more insight.
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| Clinical Risk Reclassification |
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Table 3 presents the results of risk stratification with models that include age, SBP, smoking, and total cholesterol, but with and without HDL-C. The cstatistic only changed from 0.77 to 0.78 when HDL-C was included with the other variables (Table 1, bottom), despite a relative risk of 0.54. However, of women classified at 5% to 20% 10-year risk in the model without HDL-C, >34% changed risk category when HDL-C was included in the model. More important, the new risk estimate that used HDL-C was a more accurate representation of actual risk for all but 6 of 1920 women reclassified. A similar result has been shown for the addition of C-reactive protein to models that include traditional risk factors.31 If HDL-C was not useful in risk prediction, this reclassification would occur randomly. When a completely random variable was added to the full model above, <1% were reclassified in each risk category, and roughly half of these were more accurate. When all the traditional risk factors were added to a model with age only, 7% of those at <5% risk and >60% of those at 5% risk to 20% risk were reclassified more accurately.
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To assess the potential for reclassification, risk could be estimated over a range of values of a new biomarker to determine whether it may be important to measure in an individual. Suppose that a womans age, SBP, smoking status, and total cholesterol are known, but that her HDL-C is not. Suppose that, with the assumption of a reference value for HDL-C of 50 mg/dL, her estimated 10-year risk is 8%. This could vary from about 5% for an HDL-C of 80 mg/dL to about 14% for an HDL-C of 30 mg/dL. Figure 4 shows how a womans absolute risk estimate may vary with changes in HDL-C compared with risk at the reference HDL-C of 50 mg/dL given her other risk factors. For those at low risk, the additional information is minimal, whereas for those at higher risk the impact on risk of disease is more substantial. If the difference in risk over the range of HDL-C is clinically important, then a test could be ordered to obtain the womans actual posttest probability. Although other factors such as age32 must be considered, such focus on intermediate categories of risk is an option for novel predictors or biomarkers, which are difficult or expensive to obtain.
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The estimated risk or predicted values, and how well these predict actual risk, may be a more important aspect of a prognostic model than sensitivity and specificity, on which the ROC curve is based. Even in diagnostic testing, patients (and examining physicians) are interested in whether they have the disease given a test result rather than their probability of having a positive test given the presence or absence of disease, as expressed by the sensitivity and specificity.33,34 If a patient has hypertension, he or she may not be interested in whether everyone with a myocardial infarction has hypertension, but rather his/her chances of having a myocardial infarction. The predictive value, or posttest probability, can thus be more relevant for patient care. It may be especially important for prognostic models in which the clinical question is the chance of disease development in the future given current risk factors.
| Conclusion |
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A full discussion of model fitting and validation is beyond the scope of this paper (see Harrell2), but some simple suggestions for comparison of predictive models are shown in Table 4. First, a sensitive measure, such as the likelihood ratio test, or the Bayes information criterion, should be used to determine global model fit. The Bayes information criterion applies a penalty for the number of variables and can compare models that are not nested. It is related to the posterior probability that the model is correct, and is a conservative criterion for model selection. Second, measures of calibration and discrimination, such as the Hosmer-Lemeshow statistic and the cstatistic, can be informative and should also be assessed. When these statistics give different answers, it may be that fit is better for a subset of individuals, such as those at higher risk, and predicted risks for individuals should be compared. One can determine the extent of reclassification in clinically important risk categories, and which model classifies more accurately. Finally, an important criterion for a new markers usefulness in practice is whether its measurement could lead to different treatment decisions.
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Ultimately the decision whether to include a new risk factor in prediction models depends on relative costs, both in terms of dollars and in the potential for illness prevented and lives saved.28 In the setting of prospective risk prediction, the proportion of patients reclassified correctly, rather than the cstatistic, would seem to have more relevance for such calculations. Currently, several potential biomarkers for cardiovascular risk have been proposed by various investigators. Although individual predictors may add incremental value to risk prediction, the possibilities for model improvement are greater for combinations of markers. The most promising of these novel risk factors should thus be examined rigorously and simultaneously to evaluate their potential role in improved models for clinical risk prediction.
| Acknowledgments |
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Sources of Funding
This work was supported by a grant from the Donald W. Reynolds Foundation (Las Vegas, Nevada). The Womens Health Study cohort is supported by grants (HL-43851 and CA-47988) from the National Heart Lung and Blood Institute and the National Cancer Institute, both in Bethesda, Md.
Disclosures
None.
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T. Shah, J. P Casas, J. A Cooper, I. Tzoulaki, R. Sofat, V. McCormack, L. Smeeth, J. E Deanfield, G. D Lowe, A. Rumley, et al. Critical appraisal of CRP measurement for the prediction of coronary heart disease events: new data and systematic review of 31 prospective cohorts Int. J. Epidemiol., February 1, 2009; 38(1): 217 - 231. [Abstract] [Full Text] [PDF] |
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P. M Ridker C-Reactive Protein: Eighty Years from Discovery to Emergence as a Major Risk Marker for Cardiovascular Disease Clin. Chem., February 1, 2009; 55(2): 209 - 215. [Full Text] [PDF] |
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R. S Vasan Commentary: C-reactive protein and risk prediction--moving beyond associations to assessing predictive utility and clinical usefulness Int. J. Epidemiol., February 1, 2009; 38(1): 231 - 234. [Full Text] [PDF] |
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V. Nambi, R. C. Hoogeveen, L. Chambless, Y. Hu, H. Bang, J. Coresh, H. Ni, E. Boerwinkle, T. Mosley, R. Sharrett, et al. Lipoprotein-Associated Phospholipase A2 and High-Sensitivity C-Reactive Protein Improve the Stratification of Ischemic Stroke Risk in the Atherosclerosis Risk in Communities (ARIC) Study Stroke, February 1, 2009; 40(2): 376 - 381. [Abstract] [Full Text] [PDF] |
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W. Palmas, T. G. Pickering, J. Teresi, J. E. Schwartz, A. Moran, R. S. Weinstock, and S. Shea Ambulatory Blood Pressure Monitoring and All-Cause Mortality in Elderly People With Diabetes Mellitus Hypertension, February 1, 2009; 53(2): 120 - 127. [Abstract] [Full Text] [PDF] |
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N. P. Paynter, D. I. Chasman, J. E. Buring, D. Shiffman, N. R. Cook, and P. M. Ridker Cardiovascular Disease Risk Prediction With and Without Knowledge of Genetic Variation at Chromosome 9p21.3 Ann Intern Med, January 20, 2009; 150(2): 65 - 72. [Abstract] [Full Text] [PDF] |
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W. de Ruijter, R. G J Westendorp, W. J J Assendelft, W. P J den Elzen, A. J M de Craen, S. le Cessie, and J. Gussekloo Use of Framingham risk score and new biomarkers to predict cardiovascular mortality in older people: population based observational cohort study BMJ, January 13, 2009; 338(jan08_2): a3083 - a3083. [Abstract] [Full Text] [PDF] |
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W. Gu and M. S. Pepe Estimating the capacity for improvement in risk prediction with a marker Biostat., January 1, 2009; 10(1): 172 - 186. [Abstract] [Full Text] [PDF] |
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K. Fiscella and D. Tancredi Socioeconomic Status and Coronary Heart Disease Risk Prediction JAMA, December 10, 2008; 300(22): 2666 - 2668. [Full Text] [PDF] |
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P. W.F. Wilson Progressing From Risk Factors to Omics Circ Cardiovasc Genet, December 1, 2008; 1(2): 141 - 146. [Full Text] [PDF] |
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P. M Ridker, N. P. Paynter, N. Rifai, J. M. Gaziano, and N. R. Cook C-Reactive Protein and Parental History Improve Global Cardiovascular Risk Prediction: The Reynolds Risk Score for Men Circulation, November 25, 2008; 118(22): 2243 - 2251. [Abstract] [Full Text] [PDF] |
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K. McGeechan, P. Macaskill, L. Irwig, G. Liew, and T. Y. Wong Assessing New Biomarkers and Predictive Models for Use in Clinical Practice: A Clinician's Guide Arch Intern Med, November 24, 2008; 168(21): 2304 - 2310. [Abstract] [Full Text] [PDF] |
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J. B. Meigs, P. Shrader, L. M. Sullivan, J. B. McAteer, C. S. Fox, J. Dupuis, A. K. Manning, J. C. Florez, P. W.F. Wilson, R. B. D'Agostino Sr., et al. Genotype Score in Addition to Common Risk Factors for Prediction of Type 2 Diabetes N. Engl. J. Med., November 20, 2008; 359(21): 2208 - 2219. [Abstract] [Full Text] [PDF] |
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R. M. Califf and G. S. Ginsburg Organizational Improvements to Enhance Modern Clinical Epidemiology JAMA, November 19, 2008; 300(19): 2300 - 2302. [Full Text] [PDF] |
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H. Janes, M. S. Pepe, and W. Gu Assessing the Value of Risk Predictions by Using Risk Stratification Tables Ann Intern Med, November 18, 2008; 149(10): 751 - 760. [Abstract] [Full Text] [PDF] |
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T. Pischon, H. Boeing, K. Hoffmann, M. Bergmann, M.B. Schulze, K. Overvad, Y.T. van der Schouw, E. Spencer, K.G.M. Moons, A. Tjonneland, et al. General and Abdominal Adiposity and Risk of Death in Europe N. Engl. J. Med., November 13, 2008; 359(20): 2105 - 2120. [Abstract] [Full Text] [PDF] |
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N. Sekhri, G. S Feder, C. Junghans, S. Eldridge, A. Umaipalan, R. Madhu, H. Hemingway, and A. D Timmis Incremental prognostic value of the exercise electrocardiogram in the initial assessment of patients with suspected angina: cohort study BMJ, November 13, 2008; 337(nov13_2): a2240 - a2240. [Abstract] [Full Text] [PDF] |
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C. M. Albert Prediction of Sudden Cardiac Death in Patients With Coronary Heart Disease: The Challenge Ahead Circ Cardiovasc Imaging, November 1, 2008; 1(3): 175 - 177. [Full Text] [PDF] |
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P. W.F. Wilson, M. Pencina, P. Jacques, J. Selhub, R. D'Agostino Sr, and C. J. O'Donnell C-Reactive Protein and Reclassification of Cardiovascular Risk in the Framingham Heart Study Circ Cardiovasc Qual Outcomes, November 1, 2008; 1(2): 92 - 97. [Abstract] [Full Text] [PDF] |
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H. J. Lambers Heerspink, A. H. Brantsma, D. de Zeeuw, S. J. L. Bakker, P. E. de Jong, R. T. Gansevoort, and for the PREVEND Study Group Albuminuria Assessed From First-Morning-Void Urine Samples Versus 24-Hour Urine Collections as a Predictor of Cardiovascular Morbidity and Mortality Am. J. Epidemiol., October 15, 2008; 168(8): 897 - 905. [Abstract] [Full Text] [PDF] |
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J. Cederholm, K. Eeg-Olofsson, B. Eliasson, B. Zethelius, P. M. Nilsson, S. Gudbjornsdottir, and on behalf of the Swedish National Diabetes Registe Risk Prediction of Cardiovascular Disease in Type 2 Diabetes: A risk equation from the Swedish National Diabetes Register Diabetes Care, October 1, 2008; 31(10): 2038 - 2043. [Abstract] [Full Text] [PDF] |
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S. C. Stoica, D. Kalavrouziotis, B.-J. Martin, K. J. Buth, G. M. Hirsch, J. A. Sullivan, and R. J.F. Baskett Long-Term Results of Heart Operations Performed by Surgeons-in-Training Circulation, September 30, 2008; 118(14_suppl_1): S1 - S6. [Abstract] [Full Text] [PDF] |
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M. Huelsmann, S. Neuhold, G. Strunk, D. Moertl, R. Berger, R. Prager, H. Abrahamian, M. Riedl, R. Pacher, A. Luger, et al. NT-proBNP has a high negative predictive value to rule-out short-term cardiovascular events in patients with diabetes mellitus Eur. Heart J., September 2, 2008; 29(18): 2259 - 2264. [Abstract] [Full Text] [PDF] |
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P. Prati, A. Tosetto, D. Vanuzzo, G. Bader, M. Casaroli, L. Canciani, S. Castellani, and P.-J. Touboul Carotid Intima Media Thickness and Plaques Can Predict the Occurrence of Ischemic Cerebrovascular Events Stroke, September 1, 2008; 39(9): 2470 - 2476. [Abstract] [Full Text] [PDF] |
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J.-P. Empana, F. Canoui-Poitrine, G. Luc, I. Juhan-Vague, P. Morange, D. Arveiler, J. Ferrieres, P. Amouyel, A. Bingham, M. Montaye, et al. Contribution of novel biomarkers to incident stable angina and acute coronary syndrome: the PRIME Study Eur. Heart J., August 2, 2008; 29(16): 1966 - 1974. [Abstract] [Full Text] [PDF] |
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M. S. Pepe and H. E. Janes Gauging the Performance of SNPs, Biomarkers, and Clinical Factors for Predicting Risk of Breast Cancer J Natl Cancer Inst, July 16, 2008; 100(14): 978 - 979. [Full Text] [PDF] |
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Ankle Brachial Index Collaboration Ankle Brachial Index Combined With Framingham Risk Score to Predict Cardiovascular Events and Mortality: A Meta-analysis JAMA, July 9, 2008; 300(2): 197 - 208. [Abstract] [Full Text] [PDF] |
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R. E. Gerszten, F. Accurso, G. R. Bernard, R. M. Caprioli, E. W. Klee, G. G. Klee, I. Kullo, T. A. Laguna, F. P. Roth, M. Sabatine, et al. Challenges in translating plasma proteomics from bench to bedside: update from the NHLBI Clinical Proteomics Programs Am J Physiol Lung Cell Mol Physiol, July 1, 2008; 295(1): L16 - L22. [Abstract] [Full Text] [PDF] |
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R. K. Simmons, S. Sharp, S. M. Boekholdt, L. A. Sargeant, K.-T. Khaw, N. J. Wareham, and S. J. Griffin Evaluation of the Framingham Risk Score in the European Prospective Investigation of Cancer-Norfolk Cohort: Does Adding Glycated Hemoglobin Improve the Prediction of Coronary Heart Disease Events? Arch Intern Med, June 9, 2008; 168(11): 1209 - 1216. [Abstract] [Full Text] [PDF] |
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B. Zethelius, L. Berglund, J. Sundstrom, E. Ingelsson, S. Basu, A. Larsson, P. Venge, and J. Arnlov Use of Multiple Biomarkers to Improve the Prediction of Death from Cardiovascular Causes N. Engl. J. Med., May 15, 2008; 358(20): 2107 - 2116. [Abstract] [Full Text] [PDF] |
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J. A. de Lemos and D. M. Lloyd-Jones Multiple Biomarker Panels for Cardiovascular Risk Assessment N. Engl. J. Med., May 15, 2008; 358(20): 2172 - 2174. [Full Text] [PDF] |
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R. D. Brook Potential health risks of air pollution beyond triggering acute cardiopulmonary events. JAMA, May 14, 2008; 299(18): 2194 - 2196. [Full Text] [PDF] |
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M. H. Gail, L. Bernstein, J. P. Costantino, D. Pee, and G. Ursin Response:Re: Projecting Individualized Absolute Invasive Breast Cancer Risk in African American Women J Natl Cancer Inst, May 7, 2008; 100(9): 684 - 684. [Full Text] [PDF] |
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S. S. Levinson New cardiovascular risk determinants do exist and are clinically useful Eur. Heart J., May 2, 2008; 29(10): 1335 - 1335. [Full Text] [PDF] |
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T. Leong, D. Zylberstein, I. Graham, L. Lissner, D. Ward, J. Fogarty, C. Bengtsson, C. Bjorkelund, D. Thelle, and for The Swedish-Irish-Norwegian (SIN) Collaboratio Asymmetric Dimethylarginine Independently Predicts Fatal and Nonfatal Myocardial Infarction and Stroke in Women: 24-Year Follow-Up of the Population Study of Women in Gothenburg Arterioscler. Thromb. Vasc. Biol., May 1, 2008; 28(5): 961 - 967. [Abstract] [Full Text] [PDF] |
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W. Palmas, T. G. Pickering, J. Teresi, J. E. Schwartz, L. Field, R. S. Weinstock, and S. Shea Telemedicine Home Blood Pressure Measurements and Progression of Albuminuria in Elderly People With Diabetes Hypertension, May 1, 2008; 51(5): 1282 - 1288. [Abstract] [Full Text] [PDF] |
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T. Kurth and G. Logroscino The Metabolic Syndrome: More Than the Sum of Its Components? Stroke, April 1, 2008; 39(4): 1068 - 1069. [Full Text] [PDF] |
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S. Kathiresan, O. Melander, D. Anevski, C. Guiducci, N. P. Burtt, C. Roos, J. N. Hirschhorn, G. Berglund, B. Hedblad, L. Groop, et al. Polymorphisms Associated with Cholesterol and Risk of Cardiovascular Events N. Engl. J. Med., March 20, 2008; 358(12): 1240 - 1249. [Abstract] [Full Text] [PDF] |
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J. A. Tice, S. R. Cummings, R. Smith-Bindman, L. Ichikawa, W. E. Barlow, and K. Kerlikowske Using Clinical Factors and Mammographic Breast Density to Estimate Breast Cancer Risk: Development and Validation of a New Predictive Model Ann Intern Med, March 4, 2008; 148(5): 337 - 347. [Abstract] [Full Text] [PDF] |
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J. Emmerich and P. M Ridker Can Fishing for New Genes Catch Patients at Risk of Coronary Artery Disease? Clin. Chem., March 1, 2008; 54(3): 453 - 455. [Full Text] [PDF] |
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P. J. Talmud, J. A. Cooper, J. Palmen, R. Lovering, F. Drenos, A. D. Hingorani, and S. E. Humphries Chromosome 9p21.3 Coronary Heart Disease Locus Genotype and Prospective Risk of CHD in Healthy Middle-Aged Men Clin. Chem., March 1, 2008; 54(3): 467 - 474. [Abstract] [Full Text] [PDF] |
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M. C. Fang, A. S. Go, Y. Chang, L. Borowsky, N. K. Pomernacki, D. E. Singer, and for the ATRIA Study Group Comparison of Risk Stratification Schemes to Predict Thromboembolism in People With Nonvalvular Atrial Fibrillation J. Am. Coll. Cardiol., February 26, 2008; 51(8): 810 - 815. [Abstract] [Full Text] [PDF] |
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Y. M. Smulders, A. Thijs, and J. W. Twisk New cardiovascular risk determinants do exist and are clinically useful Eur. Heart J., February 2, 2008; 29(4): 436 - 440. [Abstract] [Full Text] [PDF] |
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F. E. Dewey, J. R. Kapoor, R. S. Williams, M. J. Lipinski, E. A. Ashley, D. Hadley, J. Myers, and V. F. Froelicher Ventricular Arrhythmias During Clinical Treadmill Testing and Prognosis Arch Intern Med, January 28, 2008; 168(2): 225 - 234. [Abstract] [Full Text] [PDF] |
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N. R. Cook Statistical Evaluation of Prognostic versus Diagnostic Models: Beyond the ROC Curve Clin. Chem., January 1, 2008; 54(1): 17 - 23. [Abstract] [Full Text] [PDF] |
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P. W. Franks, R. L. Hanson, W. C. Knowler, C. Moffett, G. Enos, A. M. Infante, J. Krakoff, and H. C. Looker Childhood Predictors of Young-Onset Type 2 Diabetes Diabetes, December 1, 2007; 56(12): 2964 - 2972. [Abstract] [Full Text] [PDF] |
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J. Loscalzo Association Studies in an Era of Too Much Information: Clinical Analysis of New Biomarker and Genetic Data Circulation, October 23, 2007; 116(17): 1866 - 1870. [Full Text] [PDF] |
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T. Kempf, S. von Haehling, T. Peter, T. Allhoff, M. Cicoira, W. Doehner, P. Ponikowski, G. S. Filippatos, P. Rozentryt, H. Drexler, et al. Prognostic Utility of Growth Differentiation Factor-15 in Patients With Chronic Heart Failure J. Am. Coll. Cardiol., September 11, 2007; 50(11): 1054 - 1060. [Abstract] [Full Text] [PDF] |
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R. Latini, S. Masson, I. S. Anand, E. Missov, M. Carlson, T. Vago, L. Angelici, S. Barlera, G. Parrinello, A. P. Maggioni, et al. Prognostic Value of Very Low Plasma Concentrations of Troponin T in Patients With Stable Chronic Heart Failure Circulation, September 11, 2007; 116(11): 1242 - 1249. [Abstract] [Full Text] [PDF] |
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D. G. Hackam Predicting Stroke Risk in Patients With Atrial Fibrillation Stroke, September 1, 2007; 38(9): 2409 - 2409. [Full Text] [PDF] |
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M. S. Pepe, H. Janes, and J. W. Gu Letter by Pepe et al Regarding Article, "Use and Misuse of the Receiver Operating Characteristic Curve in Risk Prediction" Circulation, August 7, 2007; 116(6): e132 - e132. [Full Text] [PDF] |
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S.-J. Janket, Y. Shen, and J. H. Meurman Letter by Janket et al Regarding Article, "Use and Misuse of the Receiver Operating Characteristic Curve in Risk Prediction" Circulation, August 7, 2007; 116(6): e133 - e133. [Full Text] [PDF] |
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W. Koenig Cardiovascular Biomarkers: Added Value With an Integrated Approach? Circulation, July 3, 2007; 116(1): 3 - 5. [Full Text] [PDF] |
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J. J. Cao, A. M. Arnold, T. A. Manolio, J. F. Polak, B. M. Psaty, C. H. Hirsch, L. H. Kuller, and M. Cushman Association of Carotid Artery Intima-Media Thickness, Plaques, and C-Reactive Protein With Future Cardiovascular Disease and All-Cause Mortality: The Cardiovascular Health Study Circulation, July 3, 2007; 116(1): 32 - 38. [Abstract] [Full Text] [PDF] |
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P. M. Ridker C-Reactive Protein and the Prediction of Cardiovascular Events Among Those at Intermediate Risk: Moving an Inflammatory Hypothesis Toward Consensus J. Am. Coll. Cardiol., May 29, 2007; 49(21): 2129 - 2138. [Abstract] [Full Text] [PDF] |
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P. M Ridker and B. M. Everett Letter by Ridker and Everett Regarding Article, "The Inflammatory Hypothesis: Any Progress in Risk Stratification and Therapeutic Targets?" Circulation, May 22, 2007; 115(20): e475 - e475. [Full Text] [PDF] |
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M. Berkwits and E. Guallar Risk Factors, Risk Prediction, and the Apolipoprotein B-Apolipoprotein A-I Ratio Ann Intern Med, May 1, 2007; 146(9): 677 - 679. [Full Text] [PDF] |
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K. Musunuru, R. S. Blumenthal, P. M Ridker, N. R. Cook, D. M. Becker, S. Mora, D. C. Goff Jr., R. H. Fletcher, S. W. Fletcher, G. Mints, et al. Biomarkers for Prediction of Cardiovascular Events N. Engl. J. Med., April 5, 2007; 356(14): 1472 - 1475. [Full Text] [PDF] |
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D. A. Morrow and J. A. de Lemos Benchmarks for the Assessment of Novel Cardiovascular Biomarkers Circulation, February 27, 2007; 115(8): 949 - 952. [Full Text] [PDF] |
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