title: Urinary creatinine excretion, measured glomerular filtration rate and CKD outcomes.
abstract: BACKGROUND
  Muscle wasting predicts mortality in patients with end-stage renal disease (ESRD), but its role in the progression of chronic kidney disease (CKD) is uncertain. We studied CKD outcomes associated with low muscle mass, assessed by urinary creatinine excretion (UCr).
  
  
  METHODS
  The NephroTest cohort included 1429 patients with CKD stages 1-4 and both measured glomerular filtration rate (mGFR) (by (51)Cr-EDTA) and estimated glomerular filtration rate (eGFR) (by CKD-Epidemiology Collaboration equation). We used cause-specific Cox models to estimate hazard ratios (HRs) for the competing risks of ESRD and death associated with gender-specific UCr quartiles.
  
  
  RESULTS
  UCr was 13.6 ± 3.2 mmol/24 h (0.17 ± 0.05 mmol/kg/24 h) in men and 9.2 ± 2.1 (0.14 ± 0.05) in women. It was positively associated with mGFR, but not with eGFR. Over a median follow-up of 3.6 (2.1-5.8) years, 229 patients developed ESRD and 113 patients died before ESRD. Compared with patients in the highest UCr quartile, those in the lowest quartile had a higher crude HR (95% confidence interval) for pre-ESRD death: 4.3 (2.4-7.7), which was weakened, but remained statistically significant, independent of demographics, mGFR and several other factors: 2.1 (1.04-4.3). Their crude ESRD risk was not higher: HR: 0.95 (0.65-1.4), and even tended to be lower after adjusting for mGFR and log-proteinuria: HR: 0.70 (0.45-1.1). Adjustment for eGFR instead of mGFR reversed this relationship: HR: 1.7 (1.1-2.7).
  
  
  CONCLUSIONS
  In early stage CKD, low UCr is associated with higher risk for mortality, but not for ESRD. Using creatinine-based equation to adjust for GFR may bias the relationship of UCr with ESRD risk.
authors: Inserm Unit 1018, CESP, Research Centre in Epidemiology and Population Health, Villejuif, France University Paris-Sud, UMRS 1018, Villejuif, France.
authors: Elena
authors: E
authors: Tynkevich
authors: Department of Physiology, AP-HP, Hôpital Bichat, Paris, France University Paris Diderot, Paris, UMR 1149, Paris, France.
authors: Martin
authors: M
authors: Flamant
authors: Department of Physiology, AP-HP, Hôpital Tenon, Paris, France Inserm UMR-S 1155, Paris, France Paris and Sorbonne University, UPMC University-Paris 6, Paris, France.
authors: Jean-Philippe
authors: JP
authors: Haymann
authors: Inserm Unit 1018, CESP, Research Centre in Epidemiology and Population Health, Villejuif, France University Paris-Sud, UMRS 1018, Villejuif, France.
authors: Marie
authors: M
authors: Metzger
authors: Department of Nephrology, AP-HP, Hôpital Européen Georges Pompidou, Paris, France DHU Common and Rare Arterial Diseases, AP-HP, Hôpital Européen Georges Pompidou, Paris, France.
authors: Eric
authors: E
authors: Thervet
authors: Inserm UMR-S 1155, Paris, France Paris and Sorbonne University, UPMC University-Paris 6, Paris, France Department of Nephrology, AP-HP, Hôpital Tenon, Paris, France.
authors: Jean-Jacques
authors: JJ
authors: Boffa
authors: University Paris Diderot, Paris, UMR 1149, Paris, France Department of Nephrology, AP-HP, Hôpital Bichat, Paris, France.
authors: François
authors: F
authors: Vrtovsnik
authors: University Paris Descartes-Paris 5, UMRS 775, Paris, France Department of Physiology, AP-HP, Hôpital Européen Georges Pompidou, Paris, France.
authors: Pascal
authors: P
authors: Houillier
authors: Inserm Unit 1018, CESP, Research Centre in Epidemiology and Population Health, Villejuif, France.
authors: Marc
authors: M
authors: Froissart
authors: Inserm Unit 1018, CESP, Research Centre in Epidemiology and Population Health, Villejuif, France University Paris-Sud, UMRS 1018, Villejuif, France.
authors: Bénédicte
authors: B
authors: Stengel
mesh_terms: D000368:Aged; D015415:Biomarkers / Q000652:urine*; D003404:Creatinine / Q000652:urine*; D018450:Disease Progression; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D016016:Proportional Hazards Models; D011446:Prospective Studies; D011507:Proteinuria / Q000150:complications*; D051436:Renal Insufficiency, Chronic / Q000209:etiology / Q000401:mortality / Q000652:urine*; D012307:Risk Factors; D015996:Survival Rate
chemical_list: D015415:Biomarkers; D003404:Creatinine
keywords: chronic kidney disease; end-stage renal disease; glomerular filtration rate; mortality; muscle mass loss; urinary creatinine excretion