title: Is serum phosphorus control related to parathyroid hormone control in dialysis patients with secondary hyperparathyroidism?
abstract: BACKGROUND
  Elevated serum phosphorus (P) levels have been linked to increased morbidity and mortality in dialysis patients with secondary hyperparathyroidism (SHPT) but may be difficult to control if parathyroid hormone (PTH) is persistently elevated. We conducted a post hoc analysis of data from an earlier interventional study (OPTIMA) to explore the relationship between PTH control and serum P.
  
  
  METHODS
  The OPTIMA study randomized dialysis patients with intact PTH (iPTH) 300-799 pg/mL to receive conventional care alone (vitamin D and/or phosphate binders [PB]; n=184) or a cinacalcet-based regimen (n=368). For patients randomized to conventional care, investigators were allowed flexibility in using a non-cinacalcet regimen (with no specific criteria for vitamin D analogue dosage) to attain KDOQI™ targets for iPTH, P, Ca and Ca x P. For those assigned to the cinacalcet-based regimen, dosages of cinacalcet, vitamin D sterols, and PB were optimized over the first 16 weeks of the study, using a predefined treatment algorithm. The present analysis examined achievement of serum P targets (≤ 4.5 and ≤ 5.5 mg/dL) in relation to achievement of iPTH ≤ 300 pg/mL during the efficacy assessment phase (EAP; weeks 17-23).
  
  
  RESULTS
  Patients who achieved iPTH ≤ 300 pg/mL (or a reduction of ≥ 30% from baseline) were more likely to achieve serum P targets than those who did not, regardless of treatment group. Of those who did achieve iPTH ≤ 300 pg/mL, 43% achieved P ≤ 4.5 mg/dL and 70% achieved P ≤ 5.5 mg/dL, versus 21% and 46% of those who did not achieve iPTH ≤ 300 pg/mL. Doses of PB tended to be higher in patients not achieving serum P targets. Patients receiving cinacalcet were more likely to achieve iPTH ≤ 300 pg/mL than those receiving conventional care (73% vs 23% of patients). Logistic regression analysis identified lower baseline P, no PB use at baseline and cinacalcet treatment to be predictors of achieving P ≤ 4.5 mg/dL during EAP in patients above this threshold at baseline.
  
  
  CONCLUSIONS
  This post hoc analysis found that control of serum P in dialysis patients was better when serum PTH levels were lowered effectively, regardless of treatment received.
  
  
  BACKGROUND
  Clinicaltrials.gov identifier NCT00110890.
authors.affiliation: Department of Nephrology, Hospital de S, João, Medical School & Nephrology Research & Development Unit, University of Porto, Porto, Portugal. jmmdfrazao@netcabo.pt
authors.forename: João M
authors.initials: JM
authors.lastname: Frazão
authors.forename: Johann
authors.initials: J
authors.lastname: Braun
authors.forename: Piergiorgio
authors.initials: P
authors.lastname: Messa
authors.forename: Bastian
authors.initials: B
authors.lastname: Dehmel
authors.forename: Caroline
authors.initials: C
authors.lastname: Mattin
authors.forename: Martin
authors.initials: M
authors.lastname: Wilkie
mesh_terms: D000328:Adult; D000368:Aged; D015984:Causality; D015897:Comorbidity; D003956:Dialysis / Q000706:statistics & numerical data*; D005060:Europe / Q000453:epidemiology; D005260:Female; D006801:Humans; D006962:Hyperparathyroidism, Secondary / Q000097:blood* / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000097:blood*; D010758:Phosphorus / Q000097:blood*; D015995:Prevalence; D051437:Renal Insufficiency / Q000097:blood* / Q000453:epidemiology / Q000534:rehabilitation*; D012307:Risk Factors
chemical_list: D010281:Parathyroid Hormone; D010758:Phosphorus