title: Optical measurement of creatinine in spent dialysate.
abstract: OBJECTIVE
  The aim of the study was to develop an optical method for the estimation of creatinine (Cr) removal during dialysis using UV-absorbance.
  
  
  METHODS
  29 hemodialysis patients on chronic 3-times-a-week hemodialysis were studied in 6 separate studies. Double-beam pectrophotometer was used for the determination of UV-absorbance in the collected spent dialysate samples. A single wavelength (SW) and a multi-wavelength (MW) model were developed using stepwise regression utilizing Cr values from the laboratory as the dependent parameter. The reduction ratio (RR) and total removed Cr (TRCr) were estimated.
  
  
  RESULTS
  For blood-Cr RRb (mean ± SD) was 60.9 ± 5.0% (calibration set) and 58.1 ± 6.0% (validation set), for SW UVabsorbance RR_SW was 61.5 ± 5.9% and 57.3 ± 6.0%, and for MW UV-absorbance RR_MW was 65.8 ± 5.8% and 61.7 ± 6.4% respectively. RR_SW and RRb were not statistically different. RR_MW was higher compared to RRb (p < 0.05). TRCr_lab was 13.8 ± 3.8 mmol, TRCr_SW 14.5 ± 2.5 mmol and TRCr_MW 13.8 ± 2.6 mmol, being not statistically different.
  
  
  CONCLUSIONS
  In summary, creatinine removal during dialysis can be estimated as reduction ratio and total removed creatinine with the UV-absorbance technique.
authors.affiliation: Department of Biomedical Engineering, Technomedicum, Tallinn University of Technology, Tallinn, Estonia. ruth@cb.ttu.ee
authors.forename: Ruth
authors.initials: R
authors.lastname: Tomson
authors.forename: Ivo
authors.initials: I
authors.lastname: Fridolin
authors.forename: Fredrik
authors.initials: F
authors.lastname: Uhlin
authors.forename: Jana
authors.initials: J
authors.lastname: Holmar
authors.forename: Kai
authors.initials: K
authors.lastname: Lauri
authors.forename: Merike
authors.initials: M
authors.lastname: Luman
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002138:Calibration; D003404:Creatinine / Q000032:analysis* / Q000097:blood / Q000737:chemistry; D015314:Dialysis Solutions / Q000737:chemistry*; D006801:Humans; D008875:Middle Aged; D012044:Regression Analysis; D006435:Renal Dialysis / Q000379:methods*; D015203:Reproducibility of Results; D013056:Spectrophotometry, Ultraviolet / Q000379:methods*; D014527:Uric Acid / Q000032:analysis / Q000737:chemistry
chemical_list: D015314:Dialysis Solutions; D014527:Uric Acid; D003404:Creatinine