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29-01-2012 | Cardiology | Article

Coronary artery calcium testing predicts mortality in diabetes patients


Free abstract

MedWire News: Coronary artery calcium (CAC) scoring can help risk stratify individuals with diabetes, and identify patients who may benefit from therapies such as low-dose aspirin, a study shows.

The aim of the study was to evaluate whether CAC effectively stratifies individuals with diabetes across age, gender, and risk factor burden.

"This question is particularly important given recent guidelines recommending selected use of aspirin in patients with diabetes based on underlying coronary heart disease (CHD) risk," note Khurram Nasir (Yale University, New Haven, USA) and colleagues.

The researchers recruited 2384 individuals with diabetes who underwent CAC screening and followed-up the patients for a mean of 5.6 years for all-cause mortality using the Social Security Death index.

They stratified the individuals by age (<50, 50-59, and ≥60 years) and then by high-, intermediate-, and low-risk subgroups, as defined by recent guidelines detailing aspirin use in patients with diabetes.

High risk was defined as a 10-year cardiovascular disease (CVD) risk of more than 10% (men ≥50 years, women ≥60 years with ≥1 CVD risk factors) where aspirin use would be considered "reasonable." Intermediate risk was defined as a 10-year CVD risk of 5-10% (men ≥50 years, women ≥60 years without CVD risk factors) where aspirin use "may be considered." And low risk was defined as a 10-year CVD risk of less than 5% (men <50 years, women <60 years without CVD risk factors) where "aspirin should not be recommended."

As reported in Diabetes Care, the study showed that CAC was a strong predictor for mortality in each age group.

Among those aged less than 50 years with a CAC score of 0, there were no deaths per 1000 person years whereas in those with a score of 1-100, there were 7.8 deaths per 1000 person years, and in those with a score over 100 the death rate rose to 18.2 per 1000 person years. The corresponding figures in those aged 50 to 59 were 3.2, 7.3, and 16.6, respectively, and in those aged 60 or more, they were 9.9, 19.2, and 33.1.

When mortality rates by CAC score were stratified according to the criteria from the guidelines on aspirin use, individuals in the low- and intermediate-risk groups with a CAC of more than 100 had a mortality rate of more than10 deaths per 1000 person years, which the authors say is consistent with a recommendation for aspirin therapy.

Furthermore, absence of CAC among high-risk individuals translated into a low risk of 6.59 deaths per 1000 patient years.

"This suggests that even among individuals classified as high risk by age and risk factor burden, absence of CAC can identify individuals with a 10-year CVD risk of less than 10%, whose risk of bleeding from aspirin may outweigh potential benefit," writes the team.

"Definitive recommendations must come from clinical outcomes trials where treatment decisions are driven by CAC-based risk stratification," conclude Nasir et al.

By Sally Robertson

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