Development of a cardiovascular calcification index using simple imaging tools in haemodialysis patients

Abstract

Background. Coronary artery calcification (CAC) is highly prevalent in haemodialysis patients and is associated with cardiovascular outcomes. Though cardiac computed tomography (CCT) is accurate, it is not widely available. Methods. We developed a cardiovascular calcification index (CCI) to predict the presence of CAC for haemodialysis patients using simple in-office techniques. Prevalent haemodialysis patients (n = 140) underwent CCT imaging for CAC, a lateral abdominal X-ray for calcification of the abdominal aorta, an echocardiogram for valvular calcification, and pulse pressure measurement. A CCI was derived by weighting the prevalence rate ratios of CAC ≥1000. Using bootstrap techniques, validation was performed using receiver operator characteristic curves and likelihood ratios. Results. Points were assigned for patients' age (60-69 and ≥70 years, 1 and 2 points, respectively), dialysis vintage ≥2 years (1 point), aortic and mitral valve calcification (3 and 1 points, respectively), and abdominal aorta X-ray scores of 1-6 and ≥7 (2 and 4 points, respectively). Race, sex and pulse pressure did not contribute to the CCI. The CCI ranged from 0 to 11 points. The likelihood ratio of CAC ≥1000 associated with CCI scores of 2-4, 5, 6-8 and 9-11 were 1.28, 2.03, 2.94 and 3.83, respectively. Given the prevalence of CAC ≥1000 of 21% in the current study, the probability of having CAC ≥1000 was 26%, 38%, 43% and 50% for participants with CCI scores of 2-4, 5, 6-8, and ≥9, respectively. Conclusions. Although refinement is needed, the CCI developed in the current study provides an alternative for predicting CAC when CCT is not available. © 2007 Oxford University Press.