Use of biomarkers of sub-clinical infection, nutrition and neonatal maturity to interpret plasma retinol in Nigerian neonates

Using the World Health Organization criterion, the prevalence of sub-clinical vitamin A deficiency can be assessed using plasma retinol concentrations <0.7 μmol/l. However, plasma retinol can be depressed by infection; thus, the use of this criterion alone may overestimate deficiency. In the present study, we investigated the usefulness of the acute-phase proteins (APP) α(1)-antichymotrypsin (ACT) and α(1)-acid glycoprotein (AGP), plasma carotenoids and anthropometric and gestational indices to interpret plasma retinol in the blood of 192 apparently healthy Nigerian neonates collected randomly during days 1-20 postpartum. The mean weight (2.64 kg) and length (0.458 m) of the neonates and plasma concentrations (geometric mean, μmol/l) of retinol (0.54), α-carotene (0.072), β-carotene (0.076) and lutein (0.080) were low. The prevalence of vitamin A deficiency was 72%, indicating a severe public health problem. Babies who were of low birth weight (P<0.003) or premature and low birth weight (P<0.023) had significantly lower retinol concentrations than full-term normal weight babies. Thirty-two neonates had abnormal ACT and forty-four abnormal AGP concentrations. Positive correlations between retinol and ACT (r 0.186, P=0.05) and AGP (r 0.31, P=0.0001) during days 1-5 may be due to the increasing plasma retinol from maternal milk and a coincidental increasing capacity to synthesise APP. Subsequently, negative correlations between retinol and ACT (r-0.28. P=0.02) and AGP (r-0.29, P=0.018) from day 6 onwards reflected the continuing increase in plasma retinol, but no further increase in the APP. Overall, weight, ACT, lutein and age explained 30% of the variance in retinol, but lutein was the most significant (r(2) 0.18. P<0.0001). Hence, the distribution of plasma retinol concentrations in this group of neonates was more strongly linked with nutrition (via the surrogate marker lutein) than infection.