Research in context
Evidence before this study
A 2019 systematic review identified and compared the performance of 15 cardiovascular disease risk prediction models developed in diabetes populations and 11 models developed in general populations but later validated in diabetes populations. The authors found that the discriminative performance of the prediction models was only modest and only half the studies had been externally validated. They concluded that improvements in performance through the identification of additional predictors, and further validation studies, were required before the models should be implemented in clinical practice. To our knowledge, none of these studies were either conducted or validated in populations with widespread diabetes screening.
Added value of this study
By September, 2016, approximately 90% of middle-aged New Zealanders had been screened for diabetes, up from about 15% in 2001 and 50% in 2012. This followed the establishment of a national funded More Heart and Diabetes Checks health target in 2012. We are currently unaware of any other country that has diabetes screening levels as high as New Zealand. In this unique study, we were able to validate the New Zealand Diabetes Cohort Study (NZDCS) cardiovascular risk prediction equation, which was derived from a representative New Zealand diabetes population between 2000 and 2006, before the introduction of widespread diabetes screening. The NZDCS equation overestimated median cardiovascular risk by three times in woman and two times in men in a more contemporary New Zealand diabetes population recruited between 2004 and 2016, with many participants diagnosed through screening following the establishment of the 2012 health target. We then developed the world's first cardiovascular risk prediction equations in a contemporary diabetes population with almost universal diabetes screening. The new equations were well calibrated, and had a significantly improved ability to differentiate between high-risk and low-risk patients compared with the NZDCS equation.
Implications of all the available evidence
Recent widespread diabetes screening has radically changed the cardiovascular risk profile of patients with diabetes in New Zealand. The combined effect of increasing obesity, increased use of cardiovascular risk prediction equations requiring diabetes assessments, the introduction of a simple non-fasting glycated haemoglobin as the international diabetes diagnostic standard, and the development of new-generation glucose-lowering medications will inevitably lead to increased diabetes screening worldwide. We have shown that cardiovascular risk prediction equations developed before widespread diabetes screening will significantly overestimate cardiovascular risk in many screen-detected patients. Therefore, new equations, derived from diabetes populations including screen-detected patients, and with additional predictors to help to differentiate between high-risk and low-risk patients, will be required to more accurately predict cardiovascular risk in people with diabetes. Without new equations, low-risk patients might be overtreated with new-generation glucose-lowering medications that have only been shown to reduce cardiovascular events in patients at high cardiovascular risk.