Papers

Analysis of predicted coronary heart disease risk in England based on Framingham study risk appraisal models published in 1991 and 2000

Kiran Nanchahal, lecturer in medical statistics ^a, John R Duncan, statistician ^b, Paul N Durrington, professor of medicine ^c, Rodney T Jackson, professor of epidemiology ^d. 

^a Health Promotion Research Unit, Department of Public Health and Policy, London School of Hygiene and Tropical Medicine, London WC1E 7HT, ^b GlaxoSmithKline, New Frontiers Science Park, Third Avenue, Harlow CM19 5AW, ^c Clinical Research Division II, University Medical Unit, Manchester Royal Infirmary, Manchester M13 9WL, ^d Faculty of Medical and Health Sciences, University of Auckland, Grafton Mews, 52-54 Grafton Road, Auckland, New Zealand

Correspondence to: Kiran Nanchahal kiran.nanchahal{at}lshtm.ac.uk

In 2000 the UK government launched the national service framework for coronary heart disease, setting national standards for improving prevention, diagnosis, and treatment. In agreement with recent recommendations on preventing coronary heart disease¹ and managing hypertension,² this programme includes use of coronary risk appraisal models from the Framingham study published in 1991³ to help identify patients eligible for drug treatment. These models were updated in 2000,⁴ incorporating further follow up and additional risk factors. We compare the predicted risks calculated using the two models and assess the implications for preventing heart disease.

	Methods and results

Top Methods and results Comment References

The health survey for England is an annual, nationwide, household based, cross sectional survey of a representative sample of the population. We used the 1998 survey data for 5518 (62.3% of 8852) participants aged 35-74 with complete information on factors needed for assessment of coronary disease risk, after exclusion of 738 (7.7% of 9590) participants reporting angina, heart attack, or stroke diagnosed by a doctor.⁵ The 2000 models allow calculation of risk over a period of four years,⁴ whereas the 1991 models permit estimation of risk over 4-12 years.³ We estimated the 10 year and four year probabilities of developing heart disease predicted using the 1991 equations and the four year risk predicted using the 2000 equations.

Summary statistics for four year coronary disease risk per 100 population based on the 1991 and 2000 models within a range of risk categories show that both models generally produce similar distributions (table). Although substantial statistical agreement exists between classification of participants into risk categories based on the two models, participants within each category based on the 1991 models were distributed across a wide range of risk categories based on the 2000 models.

	Comment

Top Methods and results Comment References

Although population distributions of coronary risk calculated with the two models are generally similar, a significant number of people meeting criteria for drug treatment on the basis of the 1991 models would not meet the equivalent criteria on the basis of the 2000 models. Current UK guidelines generally recommend offering drug treatment for hypertension or hypercholesterolaemia to patients with a 10 year risk 15%. ^{1 2} We used a 5% risk of a coronary event in four years as being equivalent to a 10 year risk of 15%, rather than 6% over four years, because risk increases exponentially rather than linearly with age. Had we used 6%, the discrepancy between the 1991 and 2000 models would have been even greater.

Our study confirms that risk of coronary disease in Britain is high. On the basis of the 1991 risk appraisal models, approximately 32% of men and 7% of women aged 35-74 in England are at 15% risk of developing heart disease in the next 10 years. The 2000 models give figures for a four year risk 5% of 29% for men and 6% for women. Although only 1-2% of men and women ineligible for drug treatment under current criteria would be eligible if the 2000 models were used, 20% of men and 43% of women currently recommended drug treatment would not be eligible if their four year risk based on the updated models was used. Sensitivity and specificity for the 1991 risk appraisal models would be 97.6% and 90.0% for men and 79.7% and 96.0% for women, considering the updated models to provide the most up to date assessment of coronary disease risk for asymptomatic men and women. Although thresholds for drug treatment are somewhat arbitrary and depend to a large degree on the resources available, we recommend that these findings are taken into account when guidelines for coronary heart disease prevention are updated in accordance with emerging scientific evidence for statin treatment and management of mild hypertension.

	Acknowledgments

We thank J N Morris for comments on an earlier draft of the manuscript.

Contributors: KN devised this study and drafted the manuscript of the paper, JD undertook the statistical analyses, and all authors contributed to writing the paper. KN will act as guarantor.

	Footnotes

JD received a SmithKline Beecham scholarship while an MSc student at the London School of Hygiene and Tropical Medicine when some of this work was done.

Competing interests: None declared.

	References

Top Methods and results Comment References

1.	British Cardiac Society, British Hyperlipidaemia Association, British Hypertension Society, British Diabetic Association. Joint British recommendations on prevention of coronary heart disease in clinical practice. Heart 1998; 80: S1-29.
2.	Ramsay LE, Williams B, Johnston DG, MacGregor GA, Poston L, Potter JF, et al. British Hypertension Society guidelines for hypertension management 1999: summary. BMJ 1999; 319: 630-635[Free Full Text].
3.	Anderson KM, Wilson PWF, Odell PM, Kannel WB. An updated coronary risk factor profile: a statement for health professionals. Circulation 1991; 83: 356-362[Free Full Text].
4.	D'Agostino RB, Russell MW, Huse DM, Ellison C, Silbershatz H, Wilson PW, et al. Primary and subsequent coronary risk appraisal: new results from the Framingham study. Am Heart J 2000; 139: 272-281[Web of Science][Medline].
5.	Erens B, Primatesta P. Health survey for England, 1998 [computer file]. 2nd ed. Colchester, Essex: The Data Archive [distributor], 2000. [SN: 4150.]

(Accepted 13 March 2002)