Objective: To investigate the association of coronary artery calcium score with all cause mortality and cardiovascular events in people with type 2 diabetes.
Design: Systematic review and meta-analysis of observational studies.
Data sources: Studies were identified from Embase, PubMed, and abstracts from the 2011 and 2012 annual meetings of the American Diabetes Association, European Association for the Study of Diabetes, American College of Cardiology, and American Heart Association (2011).
Eligibility criteria: Prospective studies that evaluated baseline coronary artery calcium score in people with type 2 diabetes and subsequent all cause mortality or cardiovascular events (fatal and non-fatal).
Data extraction: Two independent reviewers extracted the data. The predictive value of the coronary artery calcium score was assessed by random effects model.
Results: Eight studies were included (n=6521; 802 events; mean follow-up 5.18 years). The relative risk for all cause mortality or cardiovascular events, or both comparing a total coronary artery calcium score of ≥ 10 with a score of <10 was 5.47 (95% confidence interval 2.59 to 11.53; I(2)=82.4%, P<0.001). The overall sensitivity of a total coronary artery calcium score of ≥ 10 for this composite outcome was 94% (95% confidence interval 89% to 96%), with a specificity of 34% (24% to 44%). The positive and negative likelihood ratios were 1.41 (95% confidence interval 1.20 to 1.66) and 0.18 (0.10 to 0.30), respectively. For people with a coronary artery calcium score of <10, the post-test probability of the composite outcome was about 1.8%, representing a 6.8-fold reduction from the pretest probability. Four studies evaluated cardiovascular events as the outcome (n=1805; 351 events). The relative risk for cardiovascular events comparing a total coronary artery calcium score of ≥ 10 with a score of <10 was 9.22 (2.73 to 31.07; I(2)=76.7%, P=0.005). The positive and negative likelihood ratios were 1.67 (1.30 to 2.17) and 0.11 (0.04 to 0.29), respectively.
Conclusion: In people with type 2 diabetes, a coronary artery calcium score of ≥ 10 predicts all cause mortality or cardiovascular events, or both, and cardiovascular events alone, with high sensitivity but low specificity. Clinically, the finding of a coronary artery calcium score of <10 may facilitate risk stratification by enabling the identification of people at low risk within this high risk population.