title: Evaluation of renal Kt/V as a marker of renal function in predialysis patients.
abstract: BACKGROUND
  The use of renal Kt/V (r-Kt/V) as an indicator for the need of dialysis initiation has been recommended in the NKF-DOQI guidelines. In analogy to clinical practice in peritoneal dialysis, a fall of r-Kt/V below a threshold of 2.0 per week may indicate inadequate renal toxin elimination. However, there are no studies linking r-Kt/V with other parameters of glomerular filtration rate (GFR) in predialysis patients, and the validity of r-Kt/V as parameter for timing of dialysis initiation is unknown.
  
  
  METHODS
  Renal function was assessed repeatedly in 125 patients (N = 465 measurements). In predialysis patients (r-Kt/V <2.5 per week) r-Kt/V was compared with creatinine [CCr], urea [CUr], averaged creatinine/urea clearance [CCr/Ur], Cockcroft-Gault formula [CCG], and MDRD prediction equation 6 (MDRD6-GFR). The diagnostic performance of r-Kt/V as a parameter for timing the initiation of dialysis was evaluated.
  
  
  RESULTS
  Renal Kt/V <2.5 was prevalent in 24.9% of cases (N = 116, mean 1.92 +/- 0.34). In this group mean CCr was 13.8 +/- 4.9, mean CUr 6.7 +/- 1.3, and CCr/Ur 10.2 +/- 2.9 mL/min/1.73 m2. There was no correlation of r-Kt/V with serum creatinine and MDRD6-GFR, but a significantly positive correlation with CCr/Ur (r2 = 0.3382, P < 0.001). Sensitivity of r-Kt/V to detect CCr/Ur < 10.5 mL/min/1.73 m2, defined as the threshold for dialysis initiation, was 73.6% with a specificity of 91.9%.
  
  
  CONCLUSIONS
  These results suggest that r-Kt/V is a parameter of acceptable specificity but poor sensitivity for the timing of dialysis initiation. Additional measures of renal function, such as the average of measured creatinine and urea clearance, also should be taken into consideration when deciding on the timing of dialysis initiation prior to the development of clinical signs of uremia and malnutrition.
authors.affiliation: Department of Medicine, Division of Nephrology, University of Saarland, Homburg/Saar, Germany. inmkuh@uniklinik-saarland.de
authors.forename: M K
authors.initials: MK
authors.lastname: Kuhlmann
authors.forename: M
authors.initials: M
authors.lastname: Heckmann
authors.forename: W
authors.initials: W
authors.lastname: Riegel
authors.forename: H
authors.initials: H
authors.lastname: Köhler
mesh_terms: D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000032:analysis; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007668:Kidney / Q000503:physiopathology*; D007674:Kidney Diseases / Q000503:physiopathology* / Q000628:therapy; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D017582:Renal Replacement Therapy; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014508:Urea / Q000378:metabolism*
chemical_list: D015415:Biomarkers; D014508:Urea