title: Measurement of urea nitrogen and creatinine concentrations in peritoneal dialysate and other body fluids using the Vitros analyzer.
abstract: OBJECTIVE
  A majority of chemistry analyzers have separate modes for estimating urea nitrogen and creatinine in serum and urine because of significant differences in their concentration. As there is no defined mode for other biological fluids such as dialysis fluid, these can be run on either of the two modes. On Vitros (Clinical Ortho-Diagnostics, Rochester, NY) chemistry analyzer, we observed an overestimation in calculated creatinine clearance (CrCl) and Kt/V(urea) in some children that led us to investigate into methodology used for these assays.
  
  
  METHODS
  We measured urea nitrogen and creatinine on peritoneal dialysate effluent, pleural fluid and hemofiltration effluent on serum and urine modes of Vitros analyzer.
  
  
  RESULTS
  Vitros chemistry analyzer significantly overestimated urea nitrogen and creatinine in 'urine' mode on samples with low urea nitrogen and creatinine.
  
  
  CONCLUSIONS
  Since peritoneal dialysate effluent has concentrations of urea nitrogen and creatinine comparable to serum; hence, it should be analyzed on 'serum' mode.
authors.affiliation: Section of Nephrology, Children's Mercy Hospital and University of Missouri at Kansas City, 2401 Gillham Rd., Kansas City, MO 64108, USA. tsrivastava@cmh.edu
authors.forename: Tarak
authors.initials: T
authors.lastname: Srivastava
authors.forename: Randah
authors.initials: R
authors.lastname: Althahabi
authors.forename: Uttam
authors.initials: U
authors.lastname: Garg
mesh_terms: D001826:Body Fluids / Q000378:metabolism*; D002624:Chemistry, Clinical / Q000295:instrumentation / Q000379:methods; D003404:Creatinine / Q000378:metabolism / Q000652:urine*; D015314:Dialysis Solutions / Q000737:chemistry*; D006801:Humans; D009584:Nitrogen / Q000378:metabolism / Q000652:urine*; D010530:Peritoneal Dialysis; D015203:Reproducibility of Results
chemical_list: D015314:Dialysis Solutions; D003404:Creatinine; D009584:Nitrogen