title: Estimation of the 24-h urinary protein excretion based on the estimated urinary creatinine output.
abstract: BACKGROUND
  The urinary protein/creatinine ratio [Up/Ucr (g/gCr)] has been used in the clinical management of patients with chronic kidney disease (CKD). However, a discrepancy is often noted between the Up/Ucr and 24-h urinary protein excretion [24hUp (g/day)] in patients with extremes of muscle mass. We examined devised a method for precise estimation of the 24-h urinary protein excretion (E-24hUp) based on estimation of 24-h urinary creatinine output (E-24hCr).
  
  
  METHODS
  Three parameters, spot Up/Ucr, 24hUP and E-24hUp (=Up/Ucr × E-24hCr), were determined in 116 adult patients with CKD. The correlations among the groups were analyzed.
  
  
  RESULTS
  There was a significant correlation between the Up/Ucr and 24hUp (p < 0.001). We divided the patients into three groups according to the 24hUp; the low urinary protein group (<1.0 g/day), the intermediate urinary protein group (1.0-3.5 g/day), and the high urinary protein group (>3.5 g/day). There was a significant correlation between the Up/Ucr and 24hUp in the low (p = 0.04) and high urinary protein (p = 0.01) groups, whereas the correlation coefficient was lower in the intermediate urinary protein (p = 0.07) group. Thus, we found a significant correlation between 24hUp and E-24hUp in the study population overall (p < 0.001), in the low (p = 0.01), in the intermediate (p < 0.001), and in the high urinary protein group (p < 0.001).
  
  
  CONCLUSIONS
  We conclude that a poor correlation exists between the Up/Ucr and 24hUp in patients with intermediate urinary protein excretion levels. The recommended parameter for monitoring proteinuria in such patients may be the E-24hUp, which is calculated using the E-24hCr.
authors.affiliation: Department of Medicine, Kidney Center, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjuku-ku, Tokyo, 162-8666, Japan.|Department of Nephrology, Saiseikai Kurihashi Hospital, Kuki, Saitama, Japan.
authors.forename: Masamitsu
authors.initials: M
authors.lastname: Ubukata
authors.affiliation: Department of Medicine, Kidney Center, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjuku-ku, Tokyo, 162-8666, Japan. ttakei@kc.twmu.ac.jp.|Department of Nephrology, Saiseikai Kurihashi Hospital, Kuki, Saitama, Japan. ttakei@kc.twmu.ac.jp.
authors.forename: Takashi
authors.initials: T
authors.lastname: Takei
authors.affiliation: Department of Medicine, Kidney Center, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjuku-ku, Tokyo, 162-8666, Japan.
authors.forename: Kosaku
authors.initials: K
authors.lastname: Nitta
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000652:urine; D003404:Creatinine / Q000652:urine*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007677:Kidney Function Tests; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D011237:Predictive Value of Tests; D011507:Proteinuria / Q000175:diagnosis* / Q000652:urine; D051436:Renal Insufficiency, Chronic / Q000175:diagnosis* / Q000652:urine; D013997:Time Factors; D055815:Young Adult
chemical_list: D015415:Biomarkers; D003404:Creatinine
keywords: 24-h urinary protein excretion; Estimated urinary creatinine; Protein/creatinine ratio; Urinary protein