Urinary retinol binding protein, albumin, total protein concentrations and blood electrolytes in term and preterm neonates

ABSTRACT

Fifty neonates were included in this study, divided into two groups. Group 1[control group] consisted of 22 healthy neonates. Group 1A included 12 full term, 3 females and 9 males. Their gestational ages ranged between 37-39 weeks [mean 37.58 +/- 0.76 weeks]. Group 1B included 10 preterm neonates, 4 females and 6 males. Their gestational ages ranged between 28-34 weeks [mean 30.8 +/- 2.44 weeks]. Group II included 28 sick neonates admitted to the neonatal care unit of the pediatric department of El-Menoufiya University hospital and El-Menshawy general hospital. 10 had asphyxia, 5 had pneumonia, 7 had hyaline membrane disease and 6 had acute hemolysis. All the neonates were under antibiotic therapy. Group IIA consisted of 14 full term neonates, 2 females and 12 males. Their gestational ages ranged between 37-40 weeks [mean 37.64 +/- 0.81 weeks]. Group IIB consisted of 14 preterm neonates, 3 females and 11 males. Their gestational ages ranged between 27-35 weeks [mean 30.5 +/- 2.44 weeks]. All the neonates were subjected to thorough clinical history and examination, as well as measurement of serum sodium and potassium, blood urea, serum creatinine, urinary creatinine, total protein excretion, and measurement of urinary excretion of microalbumin and retinol binding protein [RBP] in untimed urine samples by ELIZA technique. The blood urea, microalbuminuria and total proteins were significantly elevated in sick neonates [Group II] compared to healthy neonates [Group I], however the difference was not influenced by the gestational age. No significant difference could be detected in serum sodium, potassium, serum creatinine and urinary creatinine between both groups. Measurement of RBP revealed that the healthy preterm neonates [Group IB] had a significantly higher level of RBP compared to the healthy full term [Group IA, P <0.05]. Also, the sick neonates [Group II] had a significantly higher level compared to the healthy ones [Group I, P<0.01]. RBP showed a significant negative correlation with the gestational age and the Apgar score at 1 and 5 minutes, and a significant positive correlation with blood urea and microalbuminuria. Evaluating the renal function by the excretion of RBP and microalbuminuria, showed that RBP was positive in 84% of the cases while microalbuminuria was detected in 30% of the cases only. It can be concluded that Retinol binding protein is an early and specific non-invasive marker of tubular functions. It has the advantage of being able to unmask even subtle cases of kidney injury when other parameters of kidney functions are still within the normal range