Estimation of daily protein intake based on spot urine urea nitrogen concentration in chronic kidney disease patients.
BACKGROUND
Determination of daily protein intake in the management of chronic kidney disease (CKD) requires precision. Inaccuracies in recording dietary intake occur, and estimation from total urea excretion presents hurdles owing to the difficulty of collecting whole urine for 24 h. Spot urine has been used for measuring daily sodium intake and urinary protein excretion.


METHODS
In this cross-sectional study, we investigated whether urea nitrogen (UN) concentration in spot urine can be used to predict daily protein intake instead of the 24-h urine collection in 193 Japanese CKD patients (Stages G1-G5). After patient randomization into 2 datasets for the development and validation of models, bootstrapping was used to develop protein intake estimation models.


RESULTS
The parameters for the candidate multivariate regression models were male gender, age, body mass index (BMI), diabetes mellitus, dyslipidemia, proteinuria, estimated glomerular filtration rate, serum albumin level, spot urinary UN and creatinine level, and spot urinary UN/creatinine levels. The final model contained BMI and spot urinary UN level. The final model was selected because of the higher correlation between the predicted and measured protein intakes r = 0.558 (95 % confidence interval 0.400, 0.683), and the smaller distribution of the difference between the measured and predicted protein intakes than those of the other models.


CONCLUSIONS
The results suggest that UN concentration in spot urine may be used to estimate daily protein intake and that a prediction formula would be useful for nutritional control in CKD patients.
Clinical Laboratory, Tokyo Women's Medical University, Tokyo, Japan.
Hiroko
H
Kanno
Department of Nephrology, Tokyo Kyosai Hospital, Tokyo, Japan.
Eiichiro
E
Kanda
Clinical Laboratory, Tokyo Women's Medical University, Tokyo, Japan.
Asako
A
Sato
Department of Clinical Nutrition and Dietetics, Kagawa Nutrition University, Sakado, Japan.
Kaori
K
Sakamoto
Department of Nephrology, Tokyo Medical University, 6-7-1 Nishishinjuku, Shinjuku, Tokyo, 160-0023, Japan. kannoyh@tokyo-med.ac.jp.
Yoshihiko
Y
Kanno
D000328:Adult; D000368:Aged; D003430:Cross-Sectional Studies; D004044:Dietary Proteins / Q000652:urine*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D051436:Renal Insufficiency, Chronic / Q000652:urine*; D014508:Urea / Q000652:urine*
D004044:Dietary Proteins; D014508:Urea
Maroni’s formula; Protein intake; Spot urine; Urea nitrogen