Methods which use non-laboratory-based risk factors predict 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, eg, developing countries. These are the conclusions of authors of an Article in this week's edition of The Lancet.
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, a method using cheap, simple, non-lab based methods would be of great help to this strategy.
Dr Thomas Gaziano, Division of Cardiovascular Medicine, Brigham & Women's Hospital, Boston, MA, USA, and colleagues re-analysed the NHANES I study, which was a prospective cohort study of 14407 US participants aged between 25-74 years at the time they were first examined, which was between 1971-1975. The follow-up study population examined 6186 of these people, who did not report a history of cardiovascular disease (heart attack, heart failure, stroke, angina), or cancer. The lab-based method, which required blood-tests, looked at age, systolic blood pressure, smoking status, total cholesterol, reported diabetes status, and current treatment for high blood pressure. The non-lab method substituted body-mass index for cholesterol.
The researchers found there were 1529 first-time cardiovascular events- of which 578 (38%) were deaths due to cardiovascular disease - over a 21 year period. Both methods calculated a number called the c-statistic to assess cardiovascular risk prediction, and for both men and women, lab and non-lab methods gave similar c-statistics.
The authors point out that in developed countries, the added cost of cholesterol testing is about $10 for the test and an additional $20-$80 if an additional visit is needed. The costs in developing countries are $1-$3 for the test and $3-$7 for an additional visit. In India, which spends around $31 per person on health care each year, guidelines recommending cholesterol screening to risk stratify patients would need more than 10% of the entire Indian health-care budget to be devoted to this one laboratory test, which provides little or no added benefit to non-lab tests. Further, the non-lab method can obtain the required risk factor information non-invasively in just 5-10 minutes.
The authors conclude: "Although this method requires further validation and calibration, use of a simple non-laboratory approach, as suggested by WHO, could have profound effects on the affordability and availability of an adequate screening programme in developing countries. Initial screening without blood testing could lead to the quick initiation of treatment without the added cost or inconvenience of laboratory testing, and would also keep any potential loss to follow-up due to the extra step in testing to a minimum."
In an accompanying Comment, Dr Shanthi Mendis, WHO, Geneva, Switzerland, and Dr V Mohan, Madras Diabetes Research Foundation, India, caution that the conclusions for this American population may not apply to developing country populations. They say: "Although tools that use non-laboratory-based variables can help to improve affordability of screening programmes for non-communicable diseases, they should not compromise the safety of patients. For equitable care of cardiovascular disease and other major non-communicable diseases, universal access to a set of essential interventions, including laboratory assays, may be required, even in settings with limited resources."
Dr Thomas Gaziano, Division of Cardiovascular Medicine, Brigham & Women's Hospital, Boston, MA, USA T) + 1 617 676 8178 E) TGAZIANO@PARTNERS.ORG
Shanthi Mendis, WHO, Geneva, Switzerland T) +41 22795057455 E) mendiss@who.int
PDF OF ARTICLE: http://multimedia.thelancet.com/pdf/press/Labmethods.pdf
Journal
The Lancet