The impact of vascular calcification among dialysis-dependent South African patients: A 5-year follow-up study

Background: Vascular calcification is a major risk factor for cardiovascular morbidity and mortality in patients with end-stage renal disease (ESRD). In Western countries, Blacks appear to have lesser degrees of vascular calcification compared to non-Blacks. However, there is no published data from sub-Saharan Africa. Materials and methods: This study assessed the 5-year change in vascular calcification and mortality in a previously published cohort of patients with ESRD. Vascular calcification was assessed by abdominal aortic calcification score and vascular stiffness by pulse wave velocity (PWV). Results: 66 of the original 74 participants studied at baseline were identified. The median age was 46.6 years (37.6 - 59.2), and 57.6% were women. Abdominal aortic calcification showed no progression among Blacks (baseline range 0 - 5, follow-up range 0 - 8 (p = 1.00)), but a trend to progression among non-Blacks (baseline range 0 - 19, follow up range 0 - 22 (p = 0.066)). Black participants did not display a survival advantage (p = 0.870). Non-Blacks had higher parathyroidectomy rates than Blacks with 9/30 cases compared to 2/36 (p = 0.036). After adjustment for parathyroidectomy at follow-up, the odds ratio of having abdominal vascular calcification score of ≥ 1 amongst non-Blacks was 8.6-fold greater compared to Blacks (p = 0.03). A positive correlation (r = 0.5) was observed between PWV and abdominal aortic calcification (p = 0.047). Elevated baseline coronary artery calcification score and FGF-23 level at baseline were not associated with a difference in mortality. Conclusion: There was no significant progression in vascular calcification among Blacks. After adjusting for increased parathyroidectomy rates, there was a greater progression of vascular calcification amongst non-Blacks compared to Blacks.