The association of chronic kidney disease complications by albuminuria and glomerular filtration rate: a cross-sectional analysis

Background: Albuminuria is strongly associated with future risk for cardiovascular and kidney outcomes, and has been proposed to be included in the classification of chronic kidney disease (CKD) along with glomerular filtration rate (GFR). Few data are available on whether albuminuria is associated with concurrent complications of CKD. Methods: A cross-sectional analysis of 1,665 participants screened for the Modification of Diet in Renal Disease (MDRD) study was performed to examine the association between albuminuria (determined using urine albumin-creatinine ratio (ACR)) and measured GFR (determined using urinary clearance of iothalamate) with anemia, acidosis, hyperphosphatemia, and hypertension. Results: Mean GFR (± SD) was 39 ml/min/1.73 m(2) (± 21) and the median (25( )– 75(th) percentile) ACR was 161 (38 – 680) mg/g. In multivariable models adjusted for age, sex, race, kidney disease etiology, and GFR, higher ACR levels were not associated with any complication. For example, comparing ACR > 300 mg/g vs. < 30 mg/g, the prevalence ratio (95% CI) for anemia was 0.98 (0.81 – 1.20), acidosis 1.13 (0.86 – 1.48), hyperphosphatemia 1.69 (0.91 – 3.17), and hypertension 1.04 (0.97 – 1.12). Lower levels of GFR were associated with all complications. For example, GFR levels < 30 ml/min/1.73 m(2) vs. GFR levels 60 – 89 ml/min/1.73 m(2) were associated with prevalence ratios (95% CI) of anemia 4.35 (3.18 – 5.96), acidosis 5.31 (3.41 – 8.29), hyperphosphatemia 23.8 (7.71 – 73.6), and hypertension 1.21 (1.10 – 1.32). Conclusions: Albuminuria is not associated with complications after controlling for GFR in patients younger than 70 years of age with non-diabetic CKD and GFR less than 90 ml/min/1.73 m(2) and thus would not affect clinical action plans for decisions regarding evaluation and treatment of complications in similar populations.