title: Validation study of the Tanaka and Kawasaki equations to estimate the daily sodium excretion by a spot urine sample.
abstract: OBJECTIVE
  To validate Tanaka and Kawasaki's formulas to calculate the salt intake by the sodium/creatinine ratio in spot of urine.
  
  
  METHODS
  Two hundred and seventy two adults (20 - 69 years old; 52.6% women) with 24 h urine collection and two urinary spots collected on the same day (while fasting - spot 1 - or not fasting - spot 2). Anthropometry, blood pressure and fasting blood were measured on the same day. The analysis of agreement between salt consumption measured in the 24 h urine test and urinary spots were determined by the Pearson's correlation (r) and the Bland & Altman method.
  
  
  RESULTS
  The mean salt consumption measured by the 24 h sodium excretion was 10.4 ± 5.3 g/day. The correlation between the measured 24 h sodium excretion and the estimation based on spots 1 and 2, respectively, was only moderated according to Tanaka (r = 0.51 and r = 0.55; p < 0.001) and to Kawasaki (r = 0.52 and r = 0.54; p < 0.001). We observed an increasing underestimation of salt consumption by Tanaka to increasing salt consumption and conversely, an overestimation of consumption by the Kawasaki formula. The estimation of salt consumption (difference between measured and calculated salt consumption lower than 1 g/day) was adequate only when the consumption was between 9 - 12 g/day (Tanaka) and 12 - 18 g/day (Kawasaki).
  
  
  CONCLUSIONS
  Spot urine sampling is adequate to estimate salt consumption only among individuals with an actual consumption near the population mean.
authors.affiliation: Departamento de Ciências Fisiológicas, Centro de Ciências da Saúde, Universidade Federal do Espírito Santo, Vitória, ES, Brazil.
authors.forename: José Geraldo
authors.initials: JG
authors.lastname: Mill
authors.affiliation: Departamento de Ciências Fisiológicas, Centro de Ciências da Saúde, Universidade Federal do Espírito Santo, Vitória, ES, Brazil.
authors.forename: Sérgio Lamêgo
authors.initials: SL
authors.lastname: Rodrigues
authors.affiliation: Departamento de Ciências Fisiológicas, Centro de Ciências da Saúde, Universidade Federal do Espírito Santo, Vitória, ES, Brazil.
authors.forename: Marcelo Perim
authors.initials: MP
authors.lastname: Baldo
authors.affiliation: Departamento de Vigilância de Doenças e Agravos Não Transmissíveis e Promoção da Saúde, Ministério da Saúde, Brasília, DF, Brazil.
authors.forename: Deborah Carvalho
authors.initials: DC
authors.lastname: Malta
authors.affiliation: Centro de Informação Científica e Tecnológica, Fundação Oswaldo Cruz, Rio de Janeiro, RJ, Brazil.
authors.forename: Celia Landmann
authors.initials: CL
authors.lastname: Szwarcwald
mesh_terms: D000328:Adult; D000368:Aged; D005215:Fasting; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017673:Sodium Chloride, Dietary; D016482:Urinalysis; D055815:Young Adult
chemical_list: D017673:Sodium Chloride, Dietary