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

<b><i>Background:</i></b> 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. <b><i>Methods:</i></b> 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. <b><i>Results:</i></b> A significant positive correlation between GA and UC-Alb levels was found (<i>r</i>_s = 0.701, <i>p</i> &lt; 0.001, respectively). The distribution of the 5%ile of UC-Alb levels (<i>Y</i>) by GA (<i>X</i>) was approximated as a straight line (<i>Y</i> = 0.062 × <i>X</i> + 0.326, <i>R</i>² = 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. <b><i>Conclusions:</i></b> We established GA-dependent reference ranges for serum albumin levels, which may be useful to accurately diagnose hypoalbuminemia in newborns.