title: Determinants of the creatinine clearance to glomerular filtration rate ratio in patients with chronic kidney disease: a cross-sectional study.
abstract: BACKGROUND
  Creatinine secretion, as quantified by the ratio of creatinine clearance (CrCl) to glomerular filtration rate (GFR), may introduce another source of error when using serum creatinine concentration to estimate GFR. Few studies have examined determinants of the CrCl/GFR ratio. We sought to study whether higher levels of albuminuria would be associated with higher, and being non-Hispanic black with lower, CrCl/GFR ratio.
  
  
  METHODS
  We did a cross-sectional analysis of 1342 patients with chronic kidney disease from the Chronic Renal Insufficiency Cohort (CRIC) who had baseline measure of iothalamate GFR (iGFR) and 24-hour urine collections. Our predictors included urine albumin as determined from 24-hour urine collections (categorized as: <30, 30-299, 300-2999 and ≥3000 mg), and race/ethnicity (non-Hispanic white, non-Hispanic black, Hispanic). Our outcome was CrCl/iGFR ratio, a measure of creatinine secretion.
  
  
  RESULTS
  Mean iGFR was 48.0 ± 19.9 mL/min/1.73 m², median albuminuria was 84 mg per day, and 36.8% of the study participants were non-Hispanic black. Mean CrCl/iGFR ratio was 1.19 ± 0.48. There was no association between the CrCl/iGFR ratio and urine albumin (coefficient 0.11 [95% CI-0.01-0.22] for higest verus lowest levels of albuminuria, p = 0.07). Also, there was no association between race/ethnicity and CrCl/iGFR ratio (coefficient for non-Hispanic blacks was-0.03 [95% CI-0.09-0.03] compared with whites, p = 0.38).
  
  
  CONCLUSIONS
  Contrary to what had been suggested by prior smaller studies, CrCl/GFR ratio does not vary with degree of proteinuria or race/ethnicity. The ratio is also closer to 1.0 than reported by several frequently cited reports in the literature.
authors.affiliation: Division of Nephrology, Department of Internal Medicine, Taipei Medical University Hospital, Taipei, Taiwan. yclin0229@tmu.edu.tw.
authors.forename: Yen-chung
authors.initials: YC
authors.lastname: Lin
authors.forename: Nisha
authors.initials: N
authors.lastname: Bansal
authors.forename: Eric
authors.initials: E
authors.lastname: Vittinghoff
authors.forename: Alan S
authors.initials: AS
authors.lastname: Go
authors.forename: Chi-yuan
authors.initials: CY
authors.lastname: Hsu
mesh_terms: D000419:Albuminuria / Q000097:blood* / Q000175:diagnosis* / Q000453:epidemiology; D000465:Algorithms; D015897:Comorbidity; D003401:Creatine / Q000097:blood*; D003430:Cross-Sectional Studies; D003936:Diagnosis, Computer-Assisted / Q000379:methods; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007677:Kidney Function Tests / Q000379:methods*; D008297:Male; D008657:Metabolic Clearance Rate; D008875:Middle Aged; D015995:Prevalence; D051436:Renal Insufficiency, Chronic / Q000097:blood* / Q000175:diagnosis* / Q000453:epidemiology; D015203:Reproducibility of Results; D012307:Risk Factors; D012680:Sensitivity and Specificity; D014481:United States / Q000453:epidemiology
chemical_list: D003401:Creatine