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

Factors Affecting the Relationship Between Total and Unbound Bilirubin in Preterm and Term Infants

AIM

Newborn infants universally experience jaundice, most of which is physiologic, but in some high-risk situations, it may lead to neurological dysfunction or death. Unbound bilirubin (Bf) may be the best predictor of bilirubin toxicity in this population. The goal of the study is to examine the relationship between total serum bilirubin (TSB) and Bf and the influencing factors.

METHODS

To calculate the relationship of Bf to TSB, we created a ratio (R) Bf/TSB × 106 to allow the comparison of products with varied concentrations. We then applied it to simultaneously obtain TSB and Bf measurements in infants to examine the influence of prematurity, haemolysis, feeding (breast or bottle feedings) and phototherapy. We also examined R at potential toxic Bf levels in the preterm group.

RESULTS

The population consisted of 170 term and 130 preterm infants. The R was 3.64 ± 1.08 (SD) in term and 15.18 ± 9.8 in preterm infants. Prematurity and high TSB that required phototherapy significantly increased R. Higher R-values were seen at higher Bf toxic threshold levels.

CONCLUSION

An R-value can reflect the relationship between Bf and TSB. The values are greater in prematurity and in infants with high TSB, which requires phototherapy.

Umbilical cord blood as a substitute for neonatal blood in measuring serum albumin and immunoglobulin G levels

OBJECTIVES

In this study, we investigated the clinical feasibility of using umbilical cord blood as an alternative to neonatal blood for measuring serum albumin and immunoglobulin G (IgG) levels in newborns, including preterm newborns.

METHODS

Serum levels of albumin and IgG were measured in cord and neonatal blood from singleton newborns. We analyzed correlations and systematic errors between cord and neonatal blood measurements, stratifying the results for very preterm newborns (VPNs) born at a gestational age of less than 32 weeks and non-VPNs born at a gestational age of 32 weeks or later.

RESULTS

Among all 494 newborns (78 VPNs and 416 non-VPNs), serum albumin and IgG levels were determined for 95.7% and 88.7% of them, respectively. Strong correlations between cord and neonatal blood were observed for the serum albumin and IgG levels (rs = 0.864 and 0.966, respectively). Moreover, the measurement errors between cord and neonatal blood were small for all newborns (0.2 g/dL and 65 mg/dL, respectively). These findings were consistent with both VPNs and non-VPNs.

CONCLUSIONS

Umbilical cord blood is a suitable substitute for neonatal blood in measuring serum albumin and IgG levels in newborns, even in premature newborns.

Serum Albumin Assessment in Neonatal Jaundice: Impact on Phototherapy Decision-Making

OBJECTIVE

The objective of this study was to investigate the impact of serum albumin assessment on early neonatal jaundice treatment decisions.

PATIENTS AND METHODS

A retrospective review of medical records was conducted for infants of 35 weeks' gestation or more, evaluated for early neonatal jaundice in 3 hospitals in Thailand from January 1 to December 31, 2023. Per hospital protocol, serum albumin levels were routinely measured during the jaundice evaluation. Infant demographics; serum albumin; total serum bilirubin (TSB); laboratory work-up for jaundice; hyperbilirubinemia neurotoxicity risk factors; hour-specific, risk-based phototherapy threshold; and rates of phototherapy treatment were evaluated.

RESULTS

Out of 935 infants evaluated for hyperbilirubinemia, 250 infants (26.7%) had serum albumin levels less than 3.0 g/dL. Among 121 infants who received phototherapy at TSB levels meeting the guideline threshold, 49 infants had serum albumin less than 3.0 g/dL as one of the neurotoxicity risk factors. However, the decision for phototherapy would not have changed when other neurotoxicity risk factors were present, when TSB at the time of initiation of phototherapy was higher than the threshold without neurotoxicity risk factors, or when TSB at the time of cessation of phototherapy was lower than the threshold with neurotoxicity risk factors. As a result, the identification of serum albumin less than 3.0 g/dL affected phototherapy treatment decision in 16 infants (affected initiation in 13, cessation in 1, and both the initiation and cessation in 2) or 1.7% of all infants evaluated for jaundice.

CONCLUSIONS

Serum albumin levels less than 3.0 g/dL are common, affecting 1 in 4 infants assessed for jaundice. However, this has minimal impact on phototherapy decisions.

Human serum albumin: prediction model and reference values for preterm and term neonates

BACKGROUND

Human serum albumin (HSA) concentrations may alter HSA-bound drug distribution. This study aims to describe longitudinal real-world HSA trends, and to develop a prediction model for HSA concentrations using a large neonatal cohort.

METHODS

Patients admitted to the neonatal intensive care unit of the University Hospitals Leuven (postnatal age (PNA) ≤28days) were retrospectively included. Using linear mixed models, covariate effects on HSA were explored. A multivariable prediction model was developed (backward model selection procedure, 1% significance level).

RESULTS

In total, 848 neonates were included [median(interquartile range) gestational age (GA) 35(32-38)weeks, birth weight (BW) 2400(1640-3130)grams]. Median HSA concentration was 32.3(28.7-35.6)g/L. Longitudinal analyses demonstrated increasing HSA concentrations with PNA and GA for most GA groups. Univariable analyses revealed significant associations of HSA with PNA, GA, BW, current weight, total and direct bilirubin, total plasma proteins, respiratory support, mechanical ventilation, sepsis, ibuprofen use, and C-reactive protein (p-values < 0.05). A high-performance (R2 = 76.3%) multivariable HSA prediction model was developed, and PNA- and GA-dependent HSA centiles were provided.

CONCLUSION

Population-specific HSA centiles and an accurate neonatal HSA prediction model were developed, incorporating both maturational and non-maturational covariates. These results can enhance future clinical care and pharmacokinetic analyses to improve pharmacotherapy of HSA-bound drugs in neonates, respectively.

IMPACT

To improve future pharmacokinetic modeling initiatives, a high-performance human serum albumin (HSA) prediction model was developed for (pre)term neonates, using a large, single-center cohort of real-world data. This prediction model integrates both maturational and non-maturational covariates, resulting in accurate HSA predictions in neonates. Additionally, HSA centiles based on postnatal and gestational age were developed, which can be easily applied in clinical practice when interpreting HSA concentrations of neonates. In general, unbound drug fractions are higher in neonates compared to older populations. To improve pharmacotherapy of HSA-bound drugs in neonates, the obtained results can be integrated in future pharmacokinetic-pharmacodynamic analyses.

Determination and verification of reference intervals of serum immunoglobulin G at birth

BACKGROUND

To accurately assess hypogammaglobulinemia at birth, it is essential to determine the reference intervals of serum immunoglobulin (IgG) levels in newborns. In the present study, we determined the gestational age (GA)-/birth weight (BW)-dependent percentile-based reference intervals of serum IgG levels and converted them into simple formulas for practical use.

METHODS

Serum IgG levels were measured in cord blood from 2902 newborns delivered at 22 to 41 weeks of GA or 264 to 4642 g of BW after exclusion of those with congenital disorders. Linear regression analysis was used to correlate GA and UC-IgG levels and BW and UC-IgG levels. After calculation of the percentile values of UC-IgG levels for each GA or BW, the distributions were approximated by the least-squares method. Fitness was evaluated by the coefficient of determination (R2).

RESULTS

Significant positive correlations were found both between GA and UC-IgG levels (rs = 0.790, P < 0.001) and BW and UC-IgG levels (rs = 0.626, P < 0.001). The distribution of the 5%ile of UC-IgG levels (Y) by GA or BW (X) was approximated as a straight line (Y = 37.5 *X - 775.8; Y = 0.161 *X + 95.34, respectively). The fitness was stronger in the GA-derived formula than the BW-derived formula (R2 = 0.973 vs 0.913).

CONCLUSIONS

We established GA-/BW-dependent reference percentile-based intervals for serum IgG levels using cord blood from 2902 newborns without congenital disorders. Using GA-dependent reference intervals may be useful for assessing hypogammaglobulinemia at birth.