Teppei Sakoh1, Masaru Nakayama2, Shigeru Tanaka3, Ryota Yoshitomi3, Yoriko Ura1, Hitomi Nishimoto1, Akiko Fukui1, Yui Shikuwa1, Kazuhiko Tsuruya3, Takanari Kitazono3. 1. Division of Nephrology and Clinical Research Institute, Department of Internal Medicine, National Kyushu Medical Center Hospital, 1-8-1 Jigyohama, Chuo-ku, Fukuoka 810-8563, Japan. 2. Division of Nephrology and Clinical Research Institute, Department of Internal Medicine, National Kyushu Medical Center Hospital, 1-8-1 Jigyohama, Chuo-ku, Fukuoka 810-8563, Japan. Electronic address: mnaka@kyumed.jp. 3. Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
Abstract
OBJECTIVE: Serum bilirubin has been reported to be associated with the progression of kidney disease in patients with diabetic nephropathy. Less is known, however, about the relationship between bilirubin and chronic kidney disease (CKD) of other etiologies. This study was designed to clarify whether serum total bilirubin concentration is associated with kidney disease progression in patients with CKD independent of etiology. MATERIALS AND METHODS: This prospective observational study enrolled 279 consecutive patients with stages 3-5 CKD. The renal endpoint was the composite of the doubling of serum creatinine or end-stage renal disease requiring dialysis. Patients were divided into three groups by their serum total bilirubin concentrations: ≤0.3 (lowest), 0.4-0.5 (middle), and ≥0.6 (highest) mg/dL. A Cox proportional hazards model was applied to determine the risk factors for poor renal outcome. RESULTS: The median follow-up period was 21months. One-hundred and three patients reached renal end points. After multivariable adjustment, a 0.1mg/dL increase in serum bilirubin was associated negatively with poor renal outcome (hazard ratio [HR], 0.73; 95% confidence interval [CI], 0.60-0.87). In addition, after adjustment for confounding factors, including traditional and nontraditional cardiovascular risk factors, the middle (HR 3.14, 95% CI 1.36-8.57) and lowest (HR 4.22, 95% CI 1.81-11.59) bilirubin groups had significantly higher HRs for renal outcome than the highest bilirubin group. CONCLUSIONS: Lower serum bilirubin concentration was independently associated with adverse renal outcomes, suggesting that the measurement of serum bilirubin is useful for predicting kidney disease progression in patients with moderate to severe CKD.
OBJECTIVE: Serum bilirubin has been reported to be associated with the progression of kidney disease in patients with diabetic nephropathy. Less is known, however, about the relationship between bilirubin and chronic kidney disease (CKD) of other etiologies. This study was designed to clarify whether serum total bilirubin concentration is associated with kidney disease progression in patients with CKD independent of etiology. MATERIALS AND METHODS: This prospective observational study enrolled 279 consecutive patients with stages 3-5 CKD. The renal endpoint was the composite of the doubling of serum creatinine or end-stage renal disease requiring dialysis. Patients were divided into three groups by their serum total bilirubin concentrations: ≤0.3 (lowest), 0.4-0.5 (middle), and ≥0.6 (highest) mg/dL. A Cox proportional hazards model was applied to determine the risk factors for poor renal outcome. RESULTS: The median follow-up period was 21months. One-hundred and three patients reached renal end points. After multivariable adjustment, a 0.1mg/dL increase in serum bilirubin was associated negatively with poor renal outcome (hazard ratio [HR], 0.73; 95% confidence interval [CI], 0.60-0.87). In addition, after adjustment for confounding factors, including traditional and nontraditional cardiovascular risk factors, the middle (HR 3.14, 95% CI 1.36-8.57) and lowest (HR 4.22, 95% CI 1.81-11.59) bilirubin groups had significantly higher HRs for renal outcome than the highest bilirubin group. CONCLUSIONS: Lower serum bilirubin concentration was independently associated with adverse renal outcomes, suggesting that the measurement of serum bilirubin is useful for predicting kidney disease progression in patients with moderate to severe CKD.