title: Serum bilirubin: a simple routine surrogate marker of the progression of chronic kidney disease.
abstract: BACKGROUND
  Studies suggest that Chronic Kidney Disease (CKD) is a global burden health associated with significant comorbid conditions. Few biochemical parameters have gained significance in predicting the disease progression. The present work aimed to study the association of the simple biochemical parameter of serum bilirubin level with the estimated glomerular filtration rate (eGFR), and to assess their association with the co-morbid conditions in CKD.
  
  
  METHODS
  We recruited 188 patients with CKD who attended a Nephrology out-patient department. eGFR values were calculated based on the serum creatinine levels using CKD-EPI formula. Various biochemical parameters including glucose, creatinine, uric acid, total and direct bilirubin were assayed in all study subjects. Study subjects were categorized into subgroups based on their eGFR values and their diabetic status and the parameters were compared among the different subgroups.
  
  
  RESULTS
  We observed a significantly decreased serum bilirubin levels (p < 0.001) in patients with lower eGFR values, compared to those with higher eGFR levels. There was a significant positive correlation between the eGFR levels and the total bilirubin levels (r = 0.92). We also observed a significant positive correlation between the eGFR levels and the direct bilirubin levels (r = 0.76). On multivariate linear regression analysis, we found that total and direct bilirubin independently predict eGFR, after adjusting for potential confounders (p < 0.001).
  
  
  CONCLUSIONS
  Our results suggest that there is significant hypobilirubinemia in CKD, especially with increasing severity and co-existing diabetes mellitus. This finding has importance in the clinical setting, as assay of simple routine biochemical parameters such as serum bilirubin may help in predicting the early progression of CKD and more so in diabetic CKD.
authors.affiliation: a Department of Biochemistry , Jawaharlal Institute of Post Graduate Medical Education and Research , Puducherry , India.
authors.forename: K
authors.initials: K
authors.lastname: Moolchandani
authors.affiliation: a Department of Biochemistry , Jawaharlal Institute of Post Graduate Medical Education and Research , Puducherry , India.
authors.forename: M
authors.initials: M
authors.lastname: Priyadarssini
authors.affiliation: a Department of Biochemistry , Jawaharlal Institute of Post Graduate Medical Education and Research , Puducherry , India.
authors.forename: M
authors.initials: M
authors.lastname: Rajappa
authors.affiliation: b Department of Nephrology , Jawaharlal Institute of Post Graduate Medical Education and Research , Puducherry , India.
authors.forename: S
authors.initials: S
authors.lastname: Parameswaran
authors.affiliation: a Department of Biochemistry , Jawaharlal Institute of Post Graduate Medical Education and Research , Puducherry , India.
authors.forename: G
authors.initials: G
authors.lastname: Revathy
mesh_terms: D000328:Adult; D001663:Bilirubin / Q000097:blood*; D015415:Biomarkers / Q000097:blood*; D001786:Blood Glucose / Q000378:metabolism; D003404:Creatinine / Q000097:blood; D003430:Cross-Sectional Studies; D018450:Disease Progression; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011379:Prognosis; D051436:Renal Insufficiency, Chronic / Q000097:blood* / Q000473:pathology; D014527:Uric Acid / Q000097:blood
chemical_list: D015415:Biomarkers; D001786:Blood Glucose; D014527:Uric Acid; D003404:Creatinine; D001663:Bilirubin
keywords: Bilirubin; chronic kidney disease; estimated glomerular filtration rate