Evaluation of Transthyretin as a Monitor of Protein-Energy Intake in Preterm and Sick Neonatal Infants

Abstract

In the past, weight and weight gain have been the two parameters used frequently in neonatal units to monitor nutrition among high-risk infants. Our investigation sought to assess how several anthropometric measures (weight, length, head circumference, arm:head circumference ratio, and tricep skinfold) and serum albumin, transthyretin, and transferrin concentrations reflect protein and energy intake. After monitoring 42 preterm and 40 sick infants over 3 consecutive weeks, we found that transthyretin concentration proved the only serum protein which accurately measured energy and protein intakes in less than 1 week from dietary manipulation. Among preterm infants, as protein and energy intakes rose, transthyretin concentration increased significantly (p < 0.001). Preterm infants ingested 79 ± 39 kcal/kg/day and 2.04 ± 1.02 g protein/ kg/day at the first assessment point after birth and rose to 103 ± 34 kcal/kg/day and 2.64 ± 0.94 g protein/kg/day. Likewise, transthyretin measured 10.83 ± 3.91 mg/dl at the initial measurement and rose to 14.80 ± 4.44 at the second measurement time. Although protein intakes measured slightly lower in the sick group, their intakes correlated to transthyretin concentration (assessment time 1, r = 0.39; time 2, r = 0.33; time 3, r = 0.33). Thus, transthyretin concentration in neonatal infants offers a rapid, accurate, and moderately inexpensive way to monitor protein-energy adequacy. (Journal of Parenteral and Enteral Nutrition 12:162-166, 1988)