Supplementary Material for: Gestational Age-Dependent Reference Ranges for Albumin Levels in Cord Serum

Background: To diagnose hypoalbuminemia in newborns, it is essential to establish a definition applicable to those with a different gestational age (GA) and clinical conditions. A positive correlation between serum albumin levels and GA has been reported, but the study was limited to small numbers of newborns. We therefore investigated the GA-dependent reference ranges for serum albumin levels using cord venous blood (UC-Alb levels) from a large number of newborns delivered at a tertiary perinatal center. Methods: Albumin levels were assessed in 2,917 newborns at 22–41 weeks of GA after exclusion of those with congenital disorders. Linear regression analysis was used to correlate GA and UC-Alb levels. After calculation of the percentile values of UC-Alb levels for each week of GA, the distributions were approximated by the least-squares method. To validate the determined linear approximation of the 5%ile value, the UC-Alb levels in newborns with hydrops fetalis and gastroschisis were used. Results: A significant positive correlation between GA and UC-Alb levels was found (rs = 0.701, p Y) by GA (X) was approximated as a straight line (Y = 0.062 × X + 0.326, R2 = 0.951). Among the 59 and 18 newborns with hydrops fetalis and gastroschisis, 51 (86.4%) and 15 (83.3%), respectively, were below the line. Conclusions: We established GA-dependent reference ranges for serum albumin levels, which may be useful to accurately diagnose hypoalbuminemia in newborns.