title: Low serum calcium is associated with poor renal outcomes in chronic kidney disease stages 3-4 patients.
abstract: BACKGROUND
  Mineral disorders are associated with adverse renal outcomes in chronic kidney disease (CKD) patients. Previous studies have associated hypercalcemia and hypocalcemia with mortality; however, the association between serum calcium and renal outcome is not well-described. Whether adding calcium besides phosphorus or in the form of calcium-phosphorus (Ca×P) product into the model of survival analysis could improve the prediction of renal outcomes is not known.
  
  
  METHODS
  A prospective cohort of 2144 outpatients with CKD stages 3-4 was evaluated. Cox proportional hazard analysis was performed according to calcium quartiles.
  
  
  RESULTS
  The mean calcium level was 9.2±0.7 mg/dL. Low serum calcium (<9.0 mg/dL) was associated with increased risk of requiring renal replacement therapy (RRT) (hazards ratio [HR]:2.12 (95% CI: 1.49-3.02, P<0.05) and rapid renal function progression (odds ratio [OR]: 1.65 (95% CI: 1.19-2.27, P<0.05) compared with high serum calcium (>9.8 mg/dL). Adding calcium into the survival model increased the integrated discrimination improvement by 0.80% (0.12%-1.91%) while calcium-phosphorus product did not improve risk prediction.The combination of high serum phosphorus (>4.2 mg/dL) and low serum calcium (<9.1 mg/dL) was associated with the highest risk of RRT (HR:2.31 (95% CI: 1.45-3.67, P<0.05).
  
  
  CONCLUSIONS
  Low serum calcium is associated with increased risk of RRT and rapid renal function progression in CKD stage 3-4 patients. The integration of serum calcium and phosphorus, but not calcium-phosphorus product should be considered in a predictive model of renal outcome.
authors.forename: Lee-Moay
authors.initials: LM
authors.lastname: Lim
authors.forename: Hung-Tien
authors.initials: HT
authors.lastname: Kuo
authors.forename: Mei-Chuan
authors.initials: MC
authors.lastname: Kuo
authors.forename: Yi-Wen
authors.initials: YW
authors.lastname: Chiu
authors.forename: Jia-Jung
authors.initials: JJ
authors.lastname: Lee
authors.forename: Shang-Jyh
authors.initials: SJ
authors.lastname: Hwang
authors.forename: Jer-Chia
authors.initials: JC
authors.lastname: Tsai
authors.affiliation: Division of Nephrology, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung Medical University, No, 100, Tzyou 1st Road, Kaohsiung 807, Taiwan. chichi@cc.kmu.edu.tw.
authors.forename: Chi-Chih
authors.initials: CC
authors.lastname: Hung
authors.forename: Hung-Chun
authors.initials: HC
authors.lastname: Chen
mesh_terms: D000368:Aged; D002118:Calcium / Q000097:blood; D002318:Cardiovascular Diseases / Q000453:epidemiology; D012080:Chronic Kidney Disease-Mineral and Bone Disorder / Q000209:etiology; D003920:Diabetes Mellitus / Q000453:epidemiology; D005260:Female; D006801:Humans; D017379:Hypertrophy, Left Ventricular / Q000000981:diagnostic imaging / Q000209:etiology; D006996:Hypocalcemia / Q000209:etiology*; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000453:epidemiology; D010758:Phosphorus / Q000097:blood; D016016:Proportional Hazards Models; D011446:Prospective Studies; D051436:Renal Insufficiency, Chronic / Q000097:blood* / Q000401:mortality; D017582:Renal Replacement Therapy / Q000009:adverse effects; D012907:Smoking / Q000453:epidemiology; D014463:Ultrasonography
chemical_list: D010758:Phosphorus; D002118:Calcium