title: Serum phosphate and social deprivation independently predict all-cause mortality in chronic kidney disease.
abstract: BACKGROUND
  Hyperphosphataemia is linked to cardiovascular disease and mortality in chronic kidney disease (CKD). Outcome in CKD is also affected by socioeconomic status. The objective of this study was to assess the associations between serum phosphate, multiple deprivation and outcome in CKD patients.
  
  
  METHODS
  All adult patients currently not on renal replacement therapy (RRT), with first time attendance to the renal outpatient clinics in the Glasgow area between July 2010 and June 2014, were included in this prospective study. Area socioeconomic status was assessed as quintiles of the Scottish Index of Multiple Deprivation (SIMD). Outcomes were all-cause and cardiovascular mortality and commencement of RRT.
  
  
  RESULTS
  The cohort included 2950 patients with a median (interquartile range) age 67.6 (53.6-76.9) years. Median (interquartile range) eGFR was 38.1 (26.3-63.5) ml/min/1.73 m(2), mean (± standard deviation) phosphate was 1.13 (± 0.24) mmol/L and 31.6 % belonged to the most deprived quintile (SIMD quintile I). During follow-up 375 patients died and 98 commenced RRT. Phosphate ≥ 1.50 mmol/L was associated with all-cause (hazard ratio (HR) 2.51; 95 % confidence interval (CI) 1.63-3.89) and cardiovascular (HR 5.05; 95 % CI 1.90-13.46) mortality when compared to phosphate 0.90-1.09 mmol/L in multivariable analyses. SIMD quintile I was independently associated with all-cause mortality. Phosphate did not weaken the association between deprivation index and mortality, and there was no interaction between phosphate and SIMD quintiles. Neither phosphate nor SIMD predicted commencement of RRT.
  
  
  CONCLUSIONS
  Multiple deprivation and serum phosphate were strong, independent predictors of all-cause mortality in CKD and showed no interaction. Phosphate also predicted cardiovascular mortality. The results suggest that phosphate lowering should be pursued regardless of socioeconomic status.
authors.affiliation: Institute of Cardiovascular and Medical Sciences, University of Glasgow, 126 University Place, Glasgow, G12 8TA, UK. marit.solbu@unn.no.|Section of Nephrology, University Hospital of North Norway, N-9038, Tromsø, Norway. marit.solbu@unn.no.
authors.forename: Marit D
authors.initials: MD
authors.lastname: Solbu
authors.affiliation: Glasgow Renal & Transplant Unit, The Queen Elizabeth University Hospital, Glasgow, 1345 Govan Road, Glasgow, G51 4TF, UK. peter.thomson@nhs.net.
authors.forename: Peter C
authors.initials: PC
authors.lastname: Thomson
authors.affiliation: Institute of Cardiovascular and Medical Sciences, University of Glasgow, 126 University Place, Glasgow, G12 8TA, UK. sarah.macpherson2@nhs.net.
authors.forename: Sarah
authors.initials: S
authors.lastname: Macpherson
authors.affiliation: Institute of Cardiovascular and Medical Sciences, University of Glasgow, 126 University Place, Glasgow, G12 8TA, UK. Mark.Findlay@glasgow.ac.uk.|Glasgow Renal & Transplant Unit, The Queen Elizabeth University Hospital, Glasgow, 1345 Govan Road, Glasgow, G51 4TF, UK. Mark.Findlay@glasgow.ac.uk.
authors.forename: Mark D
authors.initials: MD
authors.lastname: Findlay
authors.affiliation: Institute of Cardiovascular and Medical Sciences, University of Glasgow, 126 University Place, Glasgow, G12 8TA, UK. Kate.Stevens@glasgow.ac.uk.|Glasgow Renal & Transplant Unit, The Queen Elizabeth University Hospital, Glasgow, 1345 Govan Road, Glasgow, G51 4TF, UK. Kate.Stevens@glasgow.ac.uk.
authors.forename: Kathryn K
authors.initials: KK
authors.lastname: Stevens
authors.affiliation: Institute of Cardiovascular and Medical Sciences, University of Glasgow, 126 University Place, Glasgow, G12 8TA, UK. Rajan.Patel@glasgow.ac.uk.|Glasgow Renal & Transplant Unit, The Queen Elizabeth University Hospital, Glasgow, 1345 Govan Road, Glasgow, G51 4TF, UK. Rajan.Patel@glasgow.ac.uk.
authors.forename: Rajan K
authors.initials: RK
authors.lastname: Patel
authors.affiliation: Institute of Cardiovascular and Medical Sciences, University of Glasgow, 126 University Place, Glasgow, G12 8TA, UK. Sandosh.Padmanabhan@glasgow.ac.uk.
authors.forename: Sandosh
authors.initials: S
authors.lastname: Padmanabhan
authors.affiliation: Institute of Cardiovascular and Medical Sciences, University of Glasgow, 126 University Place, Glasgow, G12 8TA, UK. Alan.Jardine@glasgow.ac.uk.|Glasgow Renal & Transplant Unit, The Queen Elizabeth University Hospital, Glasgow, 1345 Govan Road, Glasgow, G51 4TF, UK. Alan.Jardine@glasgow.ac.uk.
authors.forename: Alan G
authors.initials: AG
authors.lastname: Jardine
authors.affiliation: Institute of Cardiovascular and Medical Sciences, University of Glasgow, 126 University Place, Glasgow, G12 8TA, UK. Patrick.Mark@glasgow.ac.uk.|Glasgow Renal & Transplant Unit, The Queen Elizabeth University Hospital, Glasgow, 1345 Govan Road, Glasgow, G51 4TF, UK. Patrick.Mark@glasgow.ac.uk.
authors.forename: Patrick B
authors.initials: PB
authors.lastname: Mark
mesh_terms: D000368:Aged; D015415:Biomarkers / Q000097:blood; D015331:Cohort Studies; D015897:Comorbidity; D005260:Female; D006801:Humans; D054559:Hyperphosphatemia / Q000175:diagnosis* / Q000401:mortality* / Q000523:psychology; D015994:Incidence; D008297:Male; D008875:Middle Aged; D010710:Phosphates / Q000097:blood*; D051436:Renal Insufficiency, Chronic / Q000097:blood / Q000401:mortality* / Q000523:psychology*; D015203:Reproducibility of Results; D018570:Risk Assessment / Q000379:methods; D012606:Scotland / Q000453:epidemiology; D012680:Sensitivity and Specificity; D012934:Social Isolation / Q000523:psychology*; D016019:Survival Analysis
chemical_list: D015415:Biomarkers; D010710:Phosphates