title: Evidence that urea is a better surrogate marker of uremic toxicity than creatinine.
abstract: The protein equivalent of nitrogen appearance normalized to standard weight was determined from urea nitrogen appearance (nPNA U) and from total Kjeldahl nitrogen appearance (nPNA K) in dialysate and/or urine in 45 predialysis patients (pre D) and in 95 patients on continuous ambulatory peritoneal dialysis (CAPD). Correlations with weekly Kt/Vurea and creatinine clearance (Ccr, L/wk/1.73 m2) were determined; renal contributions of CCr in both populations were calculated both as total CCr (A) and as CCr by GFR (CCr [B], mean of renal CCr and Curea). Correlations with weekly Kt/Vurea were significant in individual (pre D:nPNA U 0.57, p < 0.01, and nPNA K 0.37, p < 0.01; CAPD:nPNA U 0.50, p < 0.01, and nPNA K 0.43, p < 0.01) and pooled populations (nPNA U 0.54, p < 0.01 and nPNA K 0.37, p < 0.01). Correlations with neither Ccr (A) nor Ccr (B) were significant. The data also allowed comment on mathematical coupling. Ccr vs nPNA K correlations share even more mathematical couplers than does the nPNA K vs Kt/Vurea correlation, yet the correlation of nPNA K with Ccr is quite low. The authors conclude that urea is a better surrogate marker of small molecular weight toxins that inhibit protein intake in uremia, and correlations of nPNA with Kt/Vurea represent more than simple mathematical coupling.
authors.affiliation: Department of Medicine, University of Missouri-Columbia 65212, USA.
authors.forename: R
authors.initials: R
authors.lastname: Mehrotra
authors.forename: R
authors.initials: R
authors.lastname: Saran
authors.forename: K D
authors.initials: KD
authors.lastname: Nolph
authors.forename: H L
authors.initials: HL
authors.lastname: Moore
authors.forename: R
authors.initials: R
authors.lastname: Khanna
mesh_terms: D015415:Biomarkers / Q000032:analysis / Q000652:urine; D003404:Creatinine / Q000378:metabolism* / Q000652:urine; D015314:Dialysis Solutions; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D010531:Peritoneal Dialysis, Continuous Ambulatory; D014118:Toxins, Biological / Q000378:metabolism / Q000652:urine; D014508:Urea / Q000378:metabolism* / Q000652:urine; D014511:Uremia / Q000378:metabolism* / Q000628:therapy / Q000652:urine
chemical_list: D015415:Biomarkers; D015314:Dialysis Solutions; D014118:Toxins, Biological; D014508:Urea; D003404:Creatinine