Association of Kidney Function and Waist Circumference with Uric Acid Levels in South Africans

Abstract

Background: Recent evidence that hyperuricemia is associated with incident chronic kidney disease (CKD) provides a potential therapeutic target for CKD that has not been explored in Africans. With hyperuricemia and gout increasing globally, we sought to determine their prevalence in South Africans with varying kidney function levels.

Methods: This was a cross-sectional study of ambulatory adult patients presenting at a General Internal Medicine Outpatients Clinic between September 2012 and March 2014. Demographic, clinical, and laboratory data collected were analyzed using STATA11. Odds ratios (ORs) and 95% confidence intervals were determined using multivariable logistic regression with bootstrapping.

Results: There were 225/261 (86.2%) black/Africans, 31/261 (11.9%) Indian South Africans, 3/261 (1.1%) Caucasians, and 2/261 (<1%) mixed ancestry South Africans. Mean age was 51.3 ± 14.5 years. Median (interquartile range) estimated glomerular filtration rate (eGFR) was 71 (38) mL/min/1.73 m² and 39.8% (104/261) of patients had CKD. Hyperuricemia prevalence was 43.7% (114/261) and increased from 16.7% in patients with eGFR ≥90 mL/min/1.73 m² to 74.2% with eGFR <30 mL/min/1.73 m² (P < 0.001). Gout prevalence was 5.4% (14/261), with equal distribution across eGFR categories (0.814). Factors independently associated with hyperuricemia were eGFR <90 [ORs 3.24 (1.15-9.14), 7.28 (2.26-23.49), and 7.88 (1.95-31.82) for eGFR 60-89.9, 30-60, and <30, respectively], albuminuria [2.32 (1.11-4.85)], and waist circumference [1.04 (1.01-1.06) per 1 cm increase]. In univariate and multivariable analysis, gout was positively associated with male gender and cardiovascular disease, while it was negatively associated with African ancestry, but none of these factors remained significant after bootstrapping; ORs 6.65 (0.64-69.24), 4.14 (0.61-28.07), and 0.18 (0.01-2.21), respectively.

Conclusion: Hyperuricemia prevalence was high, with CKD and waist circumference being the strongest predictors. Gout was uncommon in black Africans. With population data lacking, screening high-risk individuals may provide insight into the burden of hyperuricemia and gout in South Africa.

Keywords: South African; cardiovascular; chronic kidney disease; gout; hyperuricemia; waist circumference.