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2009 Roman Lecturer
From Evidence to Practice
Consensus in Cardiovascular Risk Assessment and Diabetes?
Current best practice guidelines for the assessment and management of cardiovascular risk provide an integrated approach rather than the previous approach of separate guidelines for dyslipidaemia, hypertension and diabetes. Risk assessment is based on considering all relevant risk factors and expressing cardiovascular risk in absolute terms. Decisions to treat and the intensity of treatment are based on the magnitude of absolute risk and the absolute risk reduction achievable by treating all modifiable factors, thus allowing an estimate of the number needed to treat to prevent a cardiovascular event. This is in contrast to the emphasis placed on relative risk reduction in most published research papers and clinical trials. Confusion between absolute and relative risk is common among health professionals and patients.
While the concept of absolute risk is established in best practice, the tools used to calculate this risk remain inaccurate. Most current international guidelines for the assessment of cardiovascular risk are based on conventional risk factors and use of the Framingham equation to derive an estimate of either the 5 or 10 year probability of a cardiovascular event. This is known to give poor estimates of risk in different groups, with both over and underestimation.
New prediction models are being developed which will incorporate additional variables such as family history and indices of socioeconomic deprivation. The concept of risk trajectory for younger subjects is also of interest. The use of additional ‘emerging’ biomarkers has shown little incremental value over the conventional risk factors and, in particular, trial data has not validated the usefulness of homocysteine. Constructions such as the metabolic syndrome now appear to add minimal improvement in risk prediction. hsCRP has had considerable publicity in 2008, with pressure for the analyte to be included routinely in assessment and treatment protocols but the evidence and implications for treatment have been subject to critical comment.
The role of glycaemic status in assessment of cardiovascular risk has been a matter of considerable interest. The Framingham equation is based on diabetes or no diabetes. The current diagnostic criteria for diabetes are based on old and inconsistent data and while these do identify a group at high cardiovascular risk the cut points relate primarily to prevalence of retinopathy. Similarly, therapeutic targets for HbA1c are based on trial data that showed reductions in microvascular disease. Epidemiology supports an association of glycaemic status with increased cardiovascular risk at levels well below the glucose cut points for diabetes and there is an association with HbA1c that extends through the non diabetic population range. How this data can be incorporated in risk assessment or even diagnostic criteria for diabetes is a matter under international discussion. The results of recent trials showing no cardiovascular benefit of tight glycaemic control in type 2 diabetes has provided additional controversy in this area.
The intent of the 2009 Roman Lecture is to highlight some of the issues mentioned and to stimulate discussion about implications for laboratory practice.
Dr Michael Crooke BMedSc, MBChB, PhD, FRCPA
Consultant in Chemical Pathology
Wellington Hospital
Private Bag 7902
Wellington South
New Zealand
P: +64 4 3855994
F: +64 4 3855814
E: Michael.Crooke@ccdhb.org.nz
| City | Date |
| Perth | 4 August |
| Melbourne | 6 August |
| Launceston | 8 August |
| Brisbane | 18 August |
| Adelaide | 19 August |
| Sydney | 20 August |
| Wellington | 27 August |
