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[Retinol-binding protein urinary levels in a pediatric population: evolution according to age]
M H Vaisbich1, S K Nishida, M S Silva
1Escola Paulista de Medicina - UNIFESP, São Paulo, SP, Brazil.
Insights
Urinary retinol binding-protein (RBPu) can serve as a reliable early marker for pediatric kidney tubular dysfunction. This study establishes reference intervals for RBPu in children, showing it decreases to adult levels by one month of age.
Area of Science:
- Pediatric Nephrology
- Biomarker Discovery
- Renal Physiology
Background:
- Neonatal kidneys are vulnerable to injury, impacting tubular function.
- Early detection of tubular dysfunction is crucial in pediatrics.
- Urinary retinol binding-protein (RBPu) is a potential marker for tubular injury.
Purpose of the Study:
- To establish reference intervals for RBPu in childhood.
- To investigate age-related differences in RBPu levels.
- To validate RBPu as a marker for pediatric proximal tubular dysfunction.
Main Methods:
- Studied healthy children (1 month to 8 years) and newborns (term and preterm).
- Collected urine samples for RBPu and creatinine measurement.
- Analyzed RBPu levels using logarithmic data transformation.
Main Results:
- RBPu levels in children do not follow a normal distribution.
- Established a reference interval for children >1 month: 3-269 µg/L (mean 27 µg/L).
- Newborn RBPu excretion varied but decreased to adult levels by 1 month.
Conclusions:
- RBPu is a viable, non-invasive marker for proximal tubular dysfunction in children.
- Reference intervals allow for RBPu's use in monitoring tubular injury.
- Kidney's reabsorptive capacity for RBPu matures by the first month of life.
Abstract:
OBJECTIVE: The kidney of the child, mainly the newborn, is specially susceptible to ischemic and/or toxic injuries, which can affect the renal tubular function. Therefore, reliable and precocious markers of tubular dysfunction would be useful in Pediatrics. The urinary levels of retinol binding-protein (RBPu) has been used in this way. Our goal was to evaluate the RBPu behavior in childhood to establish a reference interval and verify possible differences according to the age. METHODS: We studied healthy children aged 1 month to 8 years and healthy term and preterm babies; in the last group we only included babies without hemodynamic repercussion. We collected isolated urine samples once for children above 1 month and periodically for those below this age. In this urine, besides the dipsticks test (Combur 9(R), Boehringer), RBPu and creatinine were measured. RESULTS: We observed that the RBPu levels in childhood do not have a normal distribution; after logarithm data transformation we were able to establish an interval of reference for children above one month of age: 3 to 269 micro g/L, mean of 27 micro g/ L. In newborns, we found a large variation of RBPu excretion. However, we noticed that the excretion decreases significantly, reaching the healthy adult levels at the end of the 1st month, for term as well as for preterm newborns. CONCLUSIONS: We suggest that RBPu can be used as a marker of proximal tubular dysfunction, since we could establish an interval of reference, and it can be repeated whenever necessary in the follow-up of this kind of injury, because it is not an invasive exam. Moreover, this study contributes to the knowledge of the tubular function development for showing that at the end of the 1st month of life the newborn's kidney is able to reabsorb RBPu as the healthy adult kidney is.