Comparison of three different methods of assessing cardiovascular disease risk in New Zealanders with Type 2 diabetes mellitus.

AIM: To compare three methods of assessing 5-year absolute risk of cardiovascular disease (CVD) in adults with type 2 diabetes; the Framingham CVD equation, the UK Prospective Diabetes Study (UKPDS) coronary heart disease plus stroke equations and the New Zealand Guidelines Group (NZGG)-modified Framingham CVD equation.

METHODS: Participants were 423 people with newly (n=118) or previously diagnosed (n=305) Type 2 diabetes mellitus aged 35 to 74 years with no past history of cardiovascular disease or nephropathy from an interviewed study population of 4049 adults. Absolute 5-year CVD risks were calculated in 5-year age bands by gender; Maori, Pacific, and European ethnicity; and newly and previously diagnosed diabetes.

RESULTS: The mean 5-year CVD risk score was 2.9% (95%CI: 2.40-3.42; p<0.0001) lower for the UKPDS risk engine compared to the original Framingham equation in absolute terms, and 7.6% (95%CI: 7.05-8.08; p<0.0001) lower than the NZGG-modified Framingham equation. In general, 5-year CVD risks were highest using the NZGG-modified equation, intermediate using the original Framingham equation and lowest using the combined UKPDS coronary heart disease plus stroke equations, in all age groups by gender, ethnicity, and time of diagnosis of Type 2 diabetes. However, the 5-year CVD risks are themselves potentially low as they include treated blood pressure and lipid values. Compared to the UKPDS 15% level of risk, the NZ Guidelines modified 15% level of risk results in people with diabetes being recommended for CVD drug management 10 to 17 years earlier.

CONCLUSIONS: In general, among people with Type 2 diabetes, the Framingham equations showed higher 5-year CVD risk estimates compared to combined UKPDS coronary heart disease plus stroke equations and the NZGG-modified Framingham equation showed the highest 5-year CVD risks. In practice, people with type 2 diabetes will be managed earlier and more intensively based on their risk estimated by the current NZGG guidelines than if the UKPDS or original Framingham equations were used.