title: Direct dialysis quantification: investigation of the impact of dialysate preservation techniques on solute assays.
abstract: OBJECTIVE
  Urease-producing microorganisms may lower urea nitrogen (UN) during dialysate-side dosing. We investigated the impact of 3 proven preservatives (acetic acid, ceftazidime, thimerosal) on UN concentration, and the concentrations of creatinine (CR) and beta2-microglobulin (beta2M).
  
  
  METHODS
  The UN, CR and beta2M concentrations were assayed in 3 separate aliquots from 20 spent dialysate samples (ceftazidime, 125 mg/l, or 1% thimerosal, 1 ml/l, vs. control). The beta2M concentration was assayed in 10 further spent dialysate collections (concentrated glacial acetic acid, 5 ml/l, vs. control). Solute concentrations were compared with the concordance correlation coefficient (rc).
  
  
  RESULTS
  Ceftazidime and thimerosal had little effect on the concentrations of UN and CR (rc >0.97). For the beta2M concentration, agreement remained good (rc >0.96) for ceftazidime and thimerosal (although the former tended to lower concentrations) but acetic acid was less optimal (rc = 0.893).
  
  
  CONCLUSIONS
  Ceftazidime and thimerosal may be used as dialysate preservatives without affecting the UN or CR concentrations. Thimerosal is to be preferred when studying beta2M. Acetic acid produces unacceptable inaccuracy when measuring beta2M.
authors.affiliation: Section of Dialysis and Extracorporeal Therapy, Department of Hypertension/Nephrology, Cleveland Clinic Foundation, Cleveland, Ohio, USA. suren.kanagasundaram@nuth.nhs.uk
authors.forename: Nigel S
authors.initials: NS
authors.lastname: Kanagasundaram
authors.forename: Amy
authors.initials: A
authors.lastname: Posch
authors.forename: A Brett
authors.initials: AB
authors.lastname: Larive
authors.forename: Emil P
authors.initials: EP
authors.lastname: Paganini
authors.forename: Frederick
authors.initials: F
authors.lastname: Van Lente
mesh_terms: D019342:Acetic Acid / Q000494:pharmacology; D002442:Ceftazidime / Q000494:pharmacology; D003404:Creatinine / Q000652:urine; D015314:Dialysis Solutions / Q000737:chemistry*; D006801:Humans; D009584:Nitrogen / Q000652:urine; D011310:Preservatives, Pharmaceutical / Q000494:pharmacology*; D006435:Renal Dialysis / Q000379:methods*; D013849:Thimerosal / Q000494:pharmacology; D001613:beta 2-Microglobulin / Q000652:urine
chemical_list: D015314:Dialysis Solutions; D011310:Preservatives, Pharmaceutical; D001613:beta 2-Microglobulin; D013849:Thimerosal; D002442:Ceftazidime; D003404:Creatinine; D009584:Nitrogen; D019342:Acetic Acid