Relationship of serum bilirubin concentrations to kidney function and albuminuria in the United States adult population. Findings from the National Health and Nutrition Examination Survey 2001-2006.

Background: The association of serum bilirubin concentrations with kidney function and albuminuria has not been established in the US general population.
Methods: We performed a cross-sectional analysis of data from the National Health and Nutrition Examination Survey (NHANES) 2001-2006 and examined the associations of serum total bilirubin concentrations with estimated glomerular filtration rate (eGFR) and albuminuria in a nationally representative sample of 13,184 adults aged 20 years or older. eGFR was estimated using the abbreviated Modification of Diet in Renal Disease equation. Urinary albumin excretion was measured using the albumin/creatinine ratio.
Results: An eGFR < 60 mL/min/1.73 m(2) and urinary albumin/creatinine ratio > or = 30 mg/g were present in 8.1% (n=1072) and 10.6% (n=1402) of participants, respectively. A total of 427 (3.2%) individuals had a serum total bilirubin concentration >22.23 micromol/L. After adjustment for demographics, comorbidities, alcohol consumption, viral hepatitis status and other laboratory measures, serum bilirubin was negatively associated with eGFR, and positively with albuminuria both in the whole cohort and in the subgroup of non-diabetic individuals. In contrast, serum bilirubin was not significantly associated with eGFR or albuminuria in persons with diabetes (n=1253).
Conclusions: Increasing serum concentrations of total bilirubin are independently associated with decreasing eGFR and increasing albuminuria in the US adult population.