Introduction: Chronic kidney disease (CKD) has devastating health and social consequences for Indigenous Australians. Urine albumin-to-creatinine ratio (uACR) is a strong predictor of CKD progression in this population. The impact of hyperglycaemia on CKD progression is less well understood. We assessed how baseline glycaemic status affected CKD progression among individuals with and without albuminuria.
Methods: The eGFR Study involved 550 Indigenous Australians recruited from over 20 sites in urban, regional and remote Australia across five strata of diabetes and/or kidney function. HbA1c, serum creatinine and uACR were measured at baseline. Estimated glomerular filtration rate (eGFR) was calculated using the Chronic Kidney Disease Epidemiology Collaboration equation. Participants were classified at baseline with normoglycaemia (HbA1c 1c ≥5.7% to <6.5%; n=159) or diabetes (HbA1c ≥ 6.5% or physician-diagnosed diabetes; n=227). Linear mixed regression models were used to estimate eGFR change (ml/min per 1.73 m2 per year) for each glycaemic status group.
Results: After a median follow-up of 3.0 years the age- and sex- adjusted mean eGFR (95% CI) declined progressively among those with macroalbuminuria according to worsening glycaemia (normoglycaemia: -5.12 ml/min per 1.73m2 per year [-7.30 to -2.93]; pre-diabetes: -5.40 ml/min per 1.73m2 per year [-7.08 to -3.71]; and diabetes: -6.85 ml/min per 1.73m2 per year [-8.74 to -4.95]. eGFR decline according to glycaemic status was less consistent among those with microalbuminuria (-3.17 [-3.26 to -0.09]; -1.45 [-3.01 to 0.12] and -2.79 [-4.45 to -1.13], respectively). Among those with normal albuminuria the pattern reversed (-2.92 [-4.32 to -1.53], -1.91 [-2.63 to -1.20] and -1.17 [-1.93 to - 0.40], respectively).
Conclusion: Albuminuria was the strongest predictor of eGFR decline among this high risk Indigenous Australian population. Although eGFR decline was related to increasing glycaemia among individuals with macroalbuminuria, the pattern of eGFR decline reversed among those with normal albuminuria.