Elsevier

The Lancet

Volume 371, Issue 9616, 15–21 March 2008, Pages 923-931
The Lancet

Articles
Laboratory-based versus non-laboratory-based method for assessment of cardiovascular disease risk: the NHANES I Follow-up Study cohort

https://doi.org/10.1016/S0140-6736(08)60418-3Get rights and content

Summary

Background

Around 80% of all cardiovascular deaths occur in developing countries. Assessment of those patients at high risk is an important strategy for prevention. Since developing countries have limited resources for prevention strategies that require laboratory testing, we assessed if a risk prediction method that did not require any laboratory tests could be as accurate as one requiring laboratory information.

Methods

The National Health and Nutrition Examination Survey (NHANES) was a prospective cohort study of 14 407 US participants aged between 25–74 years at the time they were first examined (between 1971 and 1975). Our follow-up study population included participants with complete information on these surveys who did not report a history of cardiovascular disease (myocardial infarction, heart failure, stroke, angina) or cancer, yielding an analysis dataset N=6186. We compared how well either method could predict first-time fatal and non-fatal cardiovascular disease events in this cohort. For the laboratory-based model, which required blood testing, we used standard risk factors to assess risk of cardiovascular disease: age, systolic blood pressure, smoking status, total cholesterol, reported diabetes status, and current treatment for hypertension. For the non-laboratory-based model, we substituted body-mass index for cholesterol.

Findings

In the cohort of 6186, there were 1529 first-time cardiovascular events and 578 (38%) deaths due to cardiovascular disease over 21 years. In women, the laboratory-based model was useful for predicting events, with a c statistic of 0·829. The c statistic of the non-laboratory-based model was 0·831. In men, the results were similar (0·784 for the laboratory-based model and 0·783 for the non-laboratory-based model). Results were similar between the laboratory-based and non-laboratory-based models in both men and women when restricted to fatal events only.

Interpretation

A method that uses non-laboratory-based risk factors predicted cardiovascular events as accurately as one that relied on laboratory-based values. This approach could simplify risk assessment in situations where laboratory testing is inconvenient or unavailable.

Introduction

Cardiovascular disease is one of the leading causes of death worldwide,1 with 80% of cases occurring in low-income and middle-income countries.2, 3 Some developing countries spend less than US$27 per head on health care each year, compared with $3727 in high-income countries.4 Because of the limited resources available in low-income settings, finding low-cost strategies for prevention of cardiovascular disease is a priority. A well-established primary prevention strategy is to use prediction rules or risk scores to identify those at higher risk in order to target specific behavioural or drug interventions. Most risk scores have included age, sex, hypertension, smoking status, diabetes mellitus, lipid values, or family history.5, 6, 7, 8

Unfortunately, less attention has been directed at developing risk scores that would be easier to use in clinical practice without loss of predictive discrimination. In developed countries, a prediction rule that requires a laboratory test is an inconvenience; but in low-income countries, with limited testing facilities, such analysis can be too expensive to use at all. Cardiovascular disease prediction charts with and without the need for cholesterol testing for the different world regions have been released by WHO, but have not been compared with any of the standard prediction rules or validated in any cohort.9, 10, 11 In an attempt to simplify risk prediction, we assessed in a real cohort whether a prediction rule that does not need laboratory testing could predict cardiovascular disease events as effectively as one that uses laboratory-based values. Both models were assessed in the National Health and Nutrition Examination Survey (NHANES) Follow-up Study cohort.

Section snippets

Methods

We compared two risk prediction models: the laboratory-based model, which required blood testing, and the non-laboratory-based model, which required only history and physical examination measures. We compared how well either model could predict first-time fatal and non-fatal cardiovascular events in the NHANES I Epidemiologic Follow-up Study (NHEFS) cohort. In the laboratory-based model we used similar risk factors to those used in the Framingham risk score—sex, age (years), systolic blood

Results

The baseline characteristics of the population are listed in table 1. By design, the NHANES cohort was representative of the adult population in the USA. With the exception of higher rates of smoking in men and a higher proportion of women receiving treatment for hypertension, the risk factor distributions were similar between the sexes. During the 21 year follow-up, there were 44 509 person-years of follow up. Overall, there were 3400 events related to cardiovascular disease among 1529

Discussion

Our study shows that a non-laboratory-based risk method that uses information easily obtained in one outpatient visit can predict cardiovascular disease outcomes as accurately as one that requires laboratory testing. Our values of predictive discrimination of 0·83 (women) and 0·78 (men) for the non-laboratory-based model are no different than the corresponding values in the laboratory-based model. Further, this study showed that the prediction method in the NHEFS cohort using these easily

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