The bilirubin albumin ratio in the management of hyperbilirubinemia in preterm infants to improve neurodevelopmental outcome: a randomized controlled trial--BARTrial

New Roles for Albumin/Globulin Ratio in the Early-Onset Hyperbilirubinemia among Infants Born Weighing 1,000 to 2,499 Grams

INTRODUCTION

Early-onset hyperbilirubinemia (EOH) is a clinical issue for premature infants. We predicted that EOH management would be improved by fast results from common laboratory tests. Total serum bilirubin (TSB) level and the albumin/globulin ratio may contribute to improving the management of EOH.

OBJECTIVE

The aim of the study is to examine the relationship between EOH and perinatal variables among infants born weighing 1,000 to 2,499 g.

STUDY DESIGNS

A single center study was undertaken at Ohta Nishinouchi Hospital between April 1, 2016 and January 31, 2022, using blood samples prospectively collected from infants admitted to the neonatal intensive care unit that were assessed by univariate analyses and multivariate logistic regression analysis. Due to a correlation between gestational age (GA) and birth weight (BW), each variable was entered separately into Model 1 (including GA) and 2 (including BW).

RESULTS

A total of 508 infants were analyzed (270 in the non EOH group and 238 in the EOH group). No infants experienced feto-maternal transfusion syndrome or hemolytic diseases such as blood type (ABO or Rh) incompatibility or glucose-6-phosphate dehydrogenase deficiency during perinatal period. Significant relationships were observed between EOH and BW (p <0.01, odds ratio [OR], 0.997; 95% confidence interval [CI], 0.996-0.997), albumin (p <0.01, OR, 0.278; 95% CI, 0.129-0.599), albumin/globulin ratio (p <0.01, OR, 2.695; 95% CI, 1.378-5.270), TSB (p <0.01, OR, 2.774; 95% CI, 1.795-4.287), and antenatal corticoid therapy (p = 0.02, OR, 1.852; 95% CI, 1.108-3.097) in Model 2. Per receiver operating characteristic curves, an albumin/globulin ratio of 1.84 could predict EOH at a sensitivity of 50.0% and specificity of 75.6% (AUC = 0.652, p <0.01, 95% CI, 0.603-0.700).

CONCLUSION

Albumin/globulin ratio among infants born weighing 1,000 to 2,499 g may be a useful indicator of EOH.

KEY POINTS

· Early-onset hyperbilirubinemia (EOH) is a clinical issue for premature infants.. · EOH management expected to be improved through the use of common laboratory tests.. · Albumin/globulin ratio among low birth weight infants may be a useful indicator of EOH..

Hyperbilirubinemia screening and treatment in neonates born prior to 35 weeks of gestation

BACKGROUND

Guidelines on when to screen for neonatal hyperbilirubinemia apply to infants born at 35 weeks or later of gestation. It is unknown whether infants born earlier would benefit from similar guidelines. Our objective was to examine hyperbilirubinemia screening and phototherapy prescription among early preterm infants during the first 6 days of life.

METHODS

We reviewed the charts of 193 infants born prior to 35 weeks of gestation who were admitted to a tertiary care NICU in Southeastern Ontario in 2018-2019. Information on total serum bilirubin (TSB) measurements over each 12-hour interval during the first six days of life and the treatment decision (no treatment, initiate, continue, or stop phototherapy) was extracted. We also examined what proportion of infants were prescribed phototherapy during each 12-hour interval.

RESULTS

Of 1006 TSB measurements performed over the first 6 days of life, 605 were done to determine whether phototherapy should be initiated. Treatment was prescribed in 275 instances (45%). A higher proportion of infants born prior to 28 weeks of gestation required phototherapy in the first 12 hours of life (37%) compared to those born at 28-32 weeks (20%) and 33-34 weeks (5.7%).

CONCLUSIONS

Our results suggest that TSB measurements are often poorly timed to detect treatment need in infants born prior to 35 weeks of gestation. This unnecessarily increases the risk of complications from phlebotomy and is an ineffective use of health care resources. There is a need to develop guidelines to optimize hyperbilirubinemia screening among early preterm infants.

Sustained lower bilirubin-binding affinity of albumin in extremely preterm infants

BACKGROUND

Elevated albumin-free or unbound bilirubin (UB) levels beyond the first week of life have been associated with the development of bilirubin encephalopathy in preterm infants. However, the mechanism(s) that induces this prolonged unbound bilirubinemia has remained unknown. We hypothesized that it may due to a sustained lower bilirubin-binding affinity of albumin in extremely premature infants.

METHODS

Twenty-two very preterm infants born at 28-31 weeks' gestational age (GA) (VPT Group) and 21 extremely preterm infants born at 22-27 weeks' GA (EPT Group) were retrospectively studied. On days 14, 21, and 28, bilirubin-binding affinity of albumin was assessed by calculating of the UB/total bilirubin ratio, bilirubin-albumin molar ratio (BAMR), and binding affinity (Ka).

RESULTS

On days 14, 21, and 28, significantly higher UB/total bilirubin ratios were found in the EPT than in the VPT Group. Although BAMRs were comparable, significantly lower Ka values on days 14, 21, and 28 were observed in the EPT than those in the VPT Group (56.1 vs. 70.9 L/μmol, p < 0.001; 55.2 vs. 74.7 L/μmol, p < 0.001; 53.0 vs. 86.5 L/μmol, p < 0.001, respectively).

CONCLUSIONS

EPT infants have a sustained lower bilirubin-binding affinity of albumin beyond the first week of life.

IMPACT

Bilirubin encephalopathy is still reported in extremely preterm (EPT) infants. EPT infants often have prolonged unbound bilirubinemia beyond the first week of life. Sustained lower bilirubin-binding affinity of albumin, regardless of the bilirubin-albumin molar ratio (BAMR), is observed in EPT infants. BAMRs should not be used as a surrogate marker of unbound bilirubinemia, especially in EPT infants at a later postnatal period.

History and current standard of postnatal management in hemolytic disease of the fetus and newborn

Since the discovery of the Rh blood group system in 1940, a greater understanding of hemolytic disease of the fetus and newborn (HDFN) was gained. In the years thereafter, researchers and clinicians came to the current understanding that fetal and neonatal red blood cells (RBC) are hemolyzed by maternal alloantibodies directed against RBC antigens potentially leading to severe disease. Preventative measures, such as Rhesus(D) immunoprophylaxis (RhIG), have greatly decreased the prevalence of Rh(D)-mediated HDFN, although a gap between high-income countries and middle- to low-income countries was created largely due to a lack in availability and high costs of RhIG. Other important developments in the past decades have improved the identification, monitoring, and care of pregnancies, fetuses, and neonates with HDFN. Prenatally, fetal anemia may occur and intrauterine transfusions may be needed. Postnatally, pediatricians should be aware of the (antenatally determined) risk of hemolysis in RBC alloimmunization and should provide treatment for hyperbilirubinemia in the early phase and monitor for anemia in the late phase of the disease. Through this review, we aim to provide an overview of important historic events and to provide hands-on guidelines for the delivery and postnatal management of neonates with HDFN. Secondarily, we aim to describe recent scientific findings and evidence gaps.

CONCLUSION

 Multiple developments have improved the identification, monitoring, and care of pregnancies and neonates with HDFN throughout the centuries. Pediatricians should be aware of the (antenatally determined) risk of hemolysis in RBC alloimmunization and should provide treatment for hyperbilirubinemia in the early phase and monitor for late anemia in the late phase of the disease. Future studies should be set in an international setting and ultimately aim to eradicate HDFN on a global scale.

WHAT IS KNOWN

• Developments have led to a greater understanding of the pathophysiology, an improved serological identification and monitoring of at-risk cases and the current pre- and postnatal treatment.

WHAT IS NEW

• This review provides the pediatrician with hands-on guidelines for the delivery and postnatal management of neonates with HDFN. • Future studies should be set in an international setting with the ultimate aim of eradicating HDFN.

Proportion of Infant Neurodevelopment Trials Reporting a Null Finding: A Systematic Review

CONTEXT

Discovering new interventions to improve neurodevelopmental outcomes is a priority; however, clinical trials are challenging and methodological issues may impact the interpretation of intervention efficacy.

OBJECTIVES

Characterize the proportion of infant neurodevelopment trials reporting a null finding and identify features that may contribute to a null result.

DATA SOURCES

The Cochrane library, Medline, Embase, and CINAHL databases.

STUDY SELECTION

Randomized controlled trials recruiting infants aged <6 months comparing any "infant-directed" intervention against standard care, placebo, or another intervention. Neurodevelopment assessed as the primary outcome between 12 months and 10 years of age using a defined list of tools.

DATA EXTRACTION

Two reviewers independently extracted data and assessed quality of included studies.

RESULTS

Of n = 1283 records screened, 21 studies (from 20 reports) were included. Of 18 superiority studies, >70% reported a null finding. Features were identified that may have contributed to the high proportion of null findings, including selection and timing of the primary outcome measure, anticipated effect size, sample size and power, and statistical analysis methodology and rigor.

LIMITATIONS

Publication bias against null studies means the proportion of null findings is likely underestimated. Studies assessing neurodevelopment as a secondary or within a composite outcome were excluded.

CONCLUSIONS

This review identified a high proportion of infant neurodevelopmental trials that produced a null finding and detected several methodological and design considerations which may have contributed. We make several recommendations for future trials, including more sophisticated approaches to trial design, outcome assessment, and analysis.

Use of Albumin in the NICU: An Evidence-based Review

Albumin is the most abundant protein in human blood with distinctive functions throughout the human body. Low albumin levels are a predictor of mortality as well as disease outcome in children and adults. However, the clinical significance of hypoalbuminemia and the role of albumin infusions in NICUs remain unclear and controversial.

The development and validation of a predictive model for neonatal phototherapy outcome using admission indicators

Delayed exchange transfusion therapy (ETT) after phototherapy failure for newborns with severe hyperbilirubinemia could lead to serious complications such as bilirubin encephalopathy (BE). In this current manuscript we developed and validated a model using admission data for early prediction of phototherapy failure. We retrospectively examined the medical records of 292 newborns with severe hyperbilirubinemia as the training cohort and another 52 neonates as the validation cohort. Logistic regression modeling was employed to create a predictive model with seven significant admission indicators, i.e., age, past medical history, presence of hemolysis, hemoglobin, neutrophil proportion, albumin (ALB), and total serum bilirubin (TSB). To validate the model, two other models with conventional indicators were created, one incorporating the admission indicators and phototherapy failure outcome and the other using TSB decrease after phototherapy failure as a variable and phototherapy outcome as an outcome indicator. The area under the curve (AUC) of the predictive model was 0.958 [95% confidence interval (CI): 0.924-0.993] and 0.961 (95% CI: 0.914-1.000) in the training and validation cohorts, respectively. Compared with the conventional models, the new model had better predictive power and greater value for clinical decision-making by providing a possibly earlier and more accurate prediction of phototherapy failure. More rapid clinical decision-making and interventions may potentially minimize occurrence of serious complications of severe neonatal hyperbilirubinemia.

Bilirubin/albumin (B/A) ratios correlate with unbound bilirubin levels in preterm infants

BACKGROUND

A strong correlation between the bilirubin/albumin (B/A) ratio and unbound bilirubin (UB) levels in newborns ≥35 weeks of gestation has been reported. However, in preterm infants, the usefulness of B/A ratios remains unclear.

METHODS

We obtained serum from 381 newborns <35 weeks of gestation. UB levels were measured using the glucose oxidase-peroxidase method. Total serum bilirubin (TB) and albumin (Alb) concentrations were measured spectrophotometrically. Samples were then stratified into two groups based on the infant's phototherapy use. B/A ratios were calculated and correlated with UB levels. Samples taken from infants prior to or never receiving phototherapy (No PTx) were then stratified by gestational age (GA) epochs: 22-27, 28-29, 30-31, and 32-34 weeks and B/A ratios correlated with UB levels.

RESULTS

B/A ratios significantly correlated with UB levels in samples from the No PTx cohort (n = 1250; y = 1.83x - 0.15, r² = 0.93) when compared with samples from infants post-phototherapy (Post-PTx, n = 2039; y = 1.05x + 0.09, r² = 0.69). Even when stratified by GA, the correlation remained.

CONCLUSIONS

In preterm infants <35 weeks of gestation, B/A ratios correlated with UB levels better in infants prior to or never receiving phototherapy than in those infants receiving phototherapy.

IMPACT

The bilirubin/albumin (B/A) ratio significantly correlates with unbound bilirubin (UB) levels in preterm infants <35 weeks of gestation. The B/A ratio can be used as an index of UB levels in preterm infants <35 weeks of gestation. The B/A ratio is useful, especially when UB measurements are not available, for managing hyperbilirubinemia in preterm infants.

A comparison of the early motor repertoire of very preterm infants and term infants

OBJECTIVE

To obtain reference data on the early motor repertoire of very preterm infants compared with healthy term infants at three months' post-term age.

STUDY DESIGN

In this observational study, using Prechtl's method on the assessment of the early motor repertoire, we compared the quality of fidgety movements and the concurrent motor optimality score - revised of infants with a gestational age <30 weeks and/or a birth weight <1000 g with healthy infants with a gestational age of 37-42 weeks.

RESULTS

One hundred eighty very preterm and 180 healthy term infants participated. The median motor optimality scores - revised of very preterm infants were significantly lower in comparison to those of term infants, with scores of 24 (25th-75th percentiles: 23-26) and 26 (25th-75th percentiles: 26-28), respectively. Fidgety movements were aberrant (abnormal or absent) more often in very preterm infants than in term infants. The odds ratio was 4.59 (95% CI, 1.51-13.92). Compared with term infants, very preterm infants had poorer scores on the subscales age-adequate movement repertoire, observed postural patterns, and movement character with odds ratios ≥2.97. We found no differences regarding observed movement patterns.

CONCLUSION

This study provides reference data on the early motor repertoire of very preterm and healthy term infants. It demonstrates that the early motor repertoire of very preterm infants is poorer than that of term infants, a finding consistent with existing knowledge that prematurity increases the risk of poor neurodevelopment.

Bilirubin inhibits lipid raft dependent functions of L1 cell adhesion molecule in rat pup cerebellar granule neurons

BACKGROUND

The mechanism of bilirubin neurotoxicity is poorly understood. We hypothesize that bilirubin inhibits the function of lipid rafts (LR), microdomains of the plasma membrane critical for signal transduction. To test this hypothesis, we measured the effect of free bilirubin (Bf) between 7.6 and 122.5 nM on LR-dependent functions of L1 cell adhesion molecule (L1).

METHODS

Cerebellar granule neurons (CGN) were plated on poly-L-lysine overnight, and neurite length was determined after 1 h treatment with L1 alone or L1 and bilirubin. L1 activation of ERK1/2 was measured in CGN in the presence or absence of bilirubin. The effect of bilirubin on L1 distribution in LR was quantitated, and the localization of bilirubin to LR was determined.

RESULTS

The addition of bilirubin to CGN treated with L1 significantly decreased neurite length compared to L1 alone. L1 activation of ERK1/2 was inhibited by bilirubin. Bilirubin redistributed L1 into LR. Bilirubin was associated only with LR-containing fractions of a sucrose density gradient.

CONCLUSION

Bf significantly inhibits LR-dependent functions of L1 and are found only associated with LR, suggesting one mechanism by which bilirubin may exert neurotoxicity is through the dysfunction of protein-LR interactions.

IMPACT

This article establishes lipid rafts as a target for the neurotoxic effects of bilirubin. This article provides clear evidence toward establishing one mechanism of bilirubin neurotoxicity, where little is understood. This article paves the way for future investigation into lipid raft dependent functions, and its role in neurodevelopmental outcome.

Can bilirubin/albumin ratio predict neurodevelopmental outcome in severe neonatal hyperbilirubinemia? A 3-month follow up study

Background

The risk of kernicterus and BIND may be in part determined by total serum bilirubin (TSB) and by the level of non-albumin bound free bilirubin, which can easily pass the blood–brain barrier. Free bilirubin (Bf) seems a more reliable predictor for bilirubin neurotoxicity. Bilirubin/albumin ratio (B/A) is considered a surrogate parameter for Bf and has been more useful than TSB. The aim of the study is to determine whether B/A ratio correlates with BIND in newborns with severe hyperbilirubinemia and if it can predict poor neurologic outcome at 3 months follow up.

Results

This prospective study included one hundred seventeen outborn neonates ≥ 35 weeks admitted in a tertiary care neonatal intensive care unit, between May and December 2012, with TSB ≥ 20 mg/dl or necessitating exchange transfusion. Total serum bilirubin and serum albumin were done on admission and bilirubin/albumin ratio was calculated. BIND score was calculated. At the age of 3 months, 112 neonates were followed up with a detailed neurological assessment. Babies who depicted any abnormal motor examination were subjected to brain stem auditory evoked response and MRI examination. Seven infants (6.2%) presented with kernicterus on follow up. BIND scores on admission, mean TSB, and bilirubin/albumin ratio was significantly higher in kernicteric infants compared with those having normal neurological outcome at 3 months of age (P 0.001). The lowest TSB level at which kernicterus occurred in our study was 31 mg/dl. Receiver operation characteristics analysis identified B/A ratio cut off value for predicting kernicterus of 9.6 with sensitivity of 100% and specificity of 91.4%, whereas TSB cut off value of 30 mg/dl showed sensitivity of 100% and specificity of 83%.

Conclusion

B/A ratio is a strong indicator for the risk of kernicterus. B/A is more specific than TSB and should be used in the early management of neonatal hyperbilirubinemia.

Neonatal Jaundice in Preterm Infants with Bilirubin Encephalopathy

INTRODUCTION

The aim of this study is to clarify bilirubin parameters and its treatment in preterm infants with bilirubin encephalopathy (pBE).

METHODS

We asked the responders to an earlier nationwide Japanese survey on pBE to provide additional information. pBE was diagnosed based on the criteria used in the nationwide survey. We collected data on serum total bilirubin (TB), direct bilirubin (DB), albumin, and unbound bilirubin (UB) levels during the first 8 weeks of life, and on phototherapy and exchange transfusion treatments.

RESULTS

We obtained clinical data from 75 patients with pBE from 58 hospitals (response rate of 59%), who were born between 2002 and 2016. The average peak TB level was 12.6 mg/dL (215 μmol/L), and the average age at peak attainment was 19.7 days after birth. Albumin level was <2.5 g/dL in 44 patients, and the peak DB level was ≥2 mg/dL (34.2 μmol/L) in 20 patients. The average peak bilirubin/albumin (B/A) (mg/g) ratio was 3.8 (molar ratio of 0.475), and the average age at peak attainment was 18.6 days. The average peak UB level was 0.67 μg/dL (11.5 nmol/L). The median duration of phototherapy was 6 days, and the median day of the last session was 12. The peak TB level occurred after the last day of phototherapy in 30 of the 61 patients available for comparison.

CONCLUSIONS

Most patients with pBE lacked marked elevations in serum TB levels and the B/A ratio, the peaks of which were sometimes delayed to >4 weeks after birth.

Prediction of the need for phototherapy during hospital stay in preterm infants by transcutaneous bilirubinometry

BACKGROUND

Neonatal hyperbilirubinemia is a common condition that frequently requires treatment with phototherapy and less commonly by exchange transfusion, especially in preterm infants. It is important to identify and monitor infants at risk of severe unconjugated hyperbilirubinemia early in the postnatal period to instigate appropriate management plans.

AIMS

To evaluate transcutaneous bilirubinometry (TCB) as a screening tool at 24 and 48 h of age to predict the need for phototherapy during hospital stay in preterm infants.

STUDY DESIGN

A single centre prospective cohort study in a level III perinatal centre.

SUBJECTS

Preterm infants (23⁺⁰ to 36⁺⁶ weeks of gestation) were eligible for enrolment.

OUTCOME MEASURES

Primary outcome was to assess the predictive value of TCB at 24 and 48 h of age for the need of phototherapy during hospital stay.

RESULTS

A total of 338 preterm infants were enrolled. The majority of infants (98.1%) born below 32 weeks of gestation required phototherapy. For infants born at >31 + 6 weeks of gestation, TCB at 24 h of age ≥81 μmol/l had sensitivity 83%, specificity 56%, positive predictive value (PPV) 54.7% and negative predictive value (NPV) 84%. TCB at 48 h of age ≥145 μmol/l had sensitivity 65%, specificity 62%, PPV 24% and NPV 90%.

CONCLUSION

TCB performed poorly at 24 and 48 h of age as a predictor of phototherapy during hospital stay in preterm infants. The negative predictive value of the test at 48 h of age might be helpful for infants born after 31 + 6 weeks of gestation.

The role of bilirubin to albumin ratio as a predictor for mortality in critically ill patients without existing liver or biliary tract disease

Background:

Hyperbilirubinemia and hypoalbuminemia are frequently appeared and associated with poor prognosis in critically ill patients. We aim to evaluate the association between the bilirubin to albumin ratio and prognosis in intensive care unit (ICU) patients.

Methods:

This was a retrospective study of 731 patients who were admitted to the medical intensive care unit (MICU) at a tertiary-care center from July 2015 to September 2017. We analyzed the bilirubin to albumin ratio on admission to the MICU, including clinical characteristics and other examinations.

Results:

The overall 28-day survival of MICU patients was 69.1%. On univariate analysis, Acute Physiology and Chronic Health Evaluation (APACHE) II score (P<0.001), Sequential Organ Failure Assessment score (P<0.001), Simplified Acute Physiology Score II score (P<0.001), Creactive protein (P=0.015), and bilirubin/albumin ratio (P<0.001) were associated with mortality of ICU patients. The receiver operating characteristic curves for ICU patients mortality between bilirubin to albumin ratio and APACHE II score were not statistically significant (P=0.282). On multivariate analysis, higher APACHE II score (hazard ratio [HR], 1.05; 95% CI, 1.03 to 1.06; P<0.001) and bilirubin to albumin ratio (HR, 1.65; 95% CI, 1.23 to 2.20; P=0.001) were independently related to the ICU patient mortality.

Conclusions:

A higher bilirubin to albumin ratio was related to the unfavorable prognosis and mortality in critically ill patients.

Increased serum total bilirubin-albumin ratio was associated with bilirubin encephalopathy in neonates

We performed the present study to summarize the recent epidemiological characteristics of bilirubin encephalopathy and assess the role of total bilirubin-albumin ratio in the bilirubin encephalopathy. We retrospectively collected clinical data of 669 neonates with hyperbilirubinemia from the First Affiliated Hospital of Zhengzhou University between January 2015 and July 2018, including 153 neonates belonged to bilirubin encephalopathy and 516 ones were treated as control group. Compared with the control group, those with bilirubin encephalopathy have higher bilirubin-albumin ratio (13.8 ± 3.6 vs. 10.6 ± 2.5, P=0.000). The direct bilirubin and indirect bilirubin level were higher in the case group than that in the control group (P=0.000). On the contrary, the hemoglobin level was lower in the case group than that in the control group (P=0.004). There were no significant differences in gestational age (P=0.510), gender rate (P=0.313), maternal gestational diabetes ratio (P=0.071), natural childbirth ratio (P=0.686), and meconium delay (P=0.091). The results from univariate regression indicated the total bilirubin/albumin ratio was positively associated with bilirubin encephalopathy (odds ratio (OR) = 1.67, 95% confidence interval (CI): 1.59-3.14). The total bilirubin, direct bilirubin, and indirect bilirubin were also related to encephalopathy. After adjusting some potential cofounding factors, the total bilirubin-albumin was still associated with bilirubin encephalopathy. The higher total bilirubin-albumin ratio increased the risk of bilirubin encephalopathy by 23% (OR = 1.23, 95% CI: 1.16-2.48). Our results indicated that the bilirubin-albumin ratio is associated with bilirubin encephalopathy in neonates, and could be a potential predictor.

Should transcutaneous bilirubin be measured in preterm infants receiving phototherapy? The relationship between transcutaneous and total serum bilirubin in preterm infants with and without phototherapy

Our objective was to analyze the relationship between transcutaneous bilirubin (TcB) measured on an unexposed area of skin and total serum bilirubin (TSB) in preterm infants before, during, and after phototherapy (PT). For this purpose paired TSB and TcB levels were measured daily during the first ten days after birth in preterm infants of less than 32 weeks’ gestation. TcB was measured with a Dräger Jaundice Meter JM-103 on the covered hipbone. Agreement between TSB and TcB levels was assessed before, during, and after PT. True negative and corresponding false negative percentages were calculated using different TcB cut-off levels. Data are presented as mean (±SD). We obtained 856 paired TcB and TSB levels in 109 preterm infants (66 boys, gestational age 29.4 ± 1.6 weeks and birth weight 1282 g ± 316 g). We found that the difference between TSB and TcB before PT was significantly lower, 44 (±36) μmol/L, than the difference during and after PT, 61 (±29) μmol/L and 63 (±25) μmol/L, respectively; P < 0.01. Blood sampling could be reduced by 42%, with 2% false negatives, when 50 μmol/L was added to the TcB level at 70% of the PT threshold. Our conclusion is that phototherapy enhances underestimation of TSB by TcB in preterms, even if measured on unexposed skin. The use of specific TcB cut-off levels substantially reduces the need for TSB measurements.

Bilirubin binding in jaundiced newborns: from bench to bedside?

BACKGROUND

Bilirubin-induced neurologic dysfunction (BIND) is a spectrum of preventable neurological sequelae in jaundiced newborns. Current total plasma bilirubin (B_T) concentration thresholds for phototherapy and/or exchange transfusion poorly predict BIND.

METHODS

The unbound (free) bilirubin (B_f) measured at these B_T thresholds provides additional information about the risk for BIND. B_f can be readily adapted to clinical use by determining B_f population parameters at current B_T thresholds. These parameters can be established using a plasma bilirubin binding panel (BBP) consisting of B_T, B_f, and two empiric constants, the maximum B_T (B_Tmax) and the corresponding equilibrium association bilirubin constant (K).

RESULTS

B_Tmax and K provide the variables needed to accurately estimate B_f at B_T < B_Tmax to obtain B_f at threshold B_T in patient samples. Once B_f population parameters are known, the BBP in a newborn can be used to identify poor bilirubin binding (higher B_f at the threshold B_T compared with the population) and increased risk of BIND.

CONCLUSION

The BBP can also be used in jaundice screening to better identify the actual B_T at which intervention would be prudent. The BBP is used with current B_T thresholds to better identify the risk of BIND and whether and when to intervene.

Emergency release uncross-matched packed red blood cells for immediate double volume exchange transfusion in neonates with intermediate to advanced acute bilirubin encephalopathy: timely but insufficient?

Given the urgency of double volume exchange transfusion (ExT) in an infant with intermediate to advanced stages of acute bilirubin encephalopathy (ABE), it has been suggested that emergency release uncross-matched packed red blood cells (ER-PRBC) be used. The efficacy of an ExT in removing bilirubin from the brain, however, is a direct function of the mass of albumin exchanged. The very low albumin content of ER-PRBC may fail to be neuroprotective. Predicted changes in total serum bilirubin (TSB), serum albumin, the bilirubin/albumin (B/A) ratio, plasma volume (PV), and bilirubin equilibration from the extravascular space during ER-PRBC ExT are described. ExT using ER-PRBC is efficacious in lowering the TSB. However, this result is falsely reassuring as significant concurrent serum albumin loss, resultant hypoalbuminemia, contraction of PV, limited bilirubin clearance from the extravascular space, and sustained B/A ratio elevations above recommended ExT treatment thresholds suggest that bilirubin neurotoxicity will continue.

Bilirubin Albumin Binding and Unbound Unconjugated Hyperbilirubinemia in Premature Infants

OBJECTIVE

To evaluate the associations between unbound bilirubin (UB) and total serum bilirubin (TSB), bilirubin:albumin molar ratio (BAMR), and bilirubin albumin binding affinity (Ka) as a function of gestational age (GA) in infants born at 24-33 weeks GA.

STUDY DESIGN

In a prospective observational study, TSB and UB were measured twice daily at least 8 hours apart during the first postnatal week. Serum albumin was measured to calculate BAMR on each day. The highest UB on each day, corresponding TSB, and serum albumin were used to calculate the Ka on each day.

RESULTS

For the 166 infants studied, peak UB significantly correlated with concomitant Ka (r = -0.44, P = .001) but not with concomitant TSB or BAMR after adjusting for GA. On multiple regression analyses, there was a significant association of concomitant Ka (-0.06, 95% CI -0.08 to -0.04, P = .0001), but not concomitant TSB or BAMR with peak UB after controlling for GA, birth weight, race, and sex. GA group was a significant effect modifier for the association between Ka and peak UB (0.03, 95% CI 0.02-0.04, P < .001). Interaction analyses showed the association between concomitant Ka and peak UB was significant for the 24-30 weeks GA group infants, but not for the 301/7-33 weeks GA group infants.

CONCLUSIONS

Peak UB was primarily associated with a decrease in binding affinity in infants ≤30 weeks GA. Interventions aimed at improving binding affinity may be important in decreasing the risk of bilirubin-induced neurotoxicity.

Prevalence of Hypoalbuminemia and Elevated Bilirubin/Albumin Ratios in a Large Cohort of Infants in the Neonatal Intensive Care Unit

OBJECTIVE

To provide descriptive data on serum albumin levels and the bilirubin to albumin (B/A) ratio in neonates admitted to the neonatal intensive care unit, assess the effect of gestational and chronological age on serum albumin and the B/A ratio, and evaluate the association between extreme values and mortality.

STUDY DESIGN

Using a retrospective cohort design, we queried the Pediatrix clinical data warehouse for all infants born between 23 and 41 weeks of gestation from 1997 to 2014 who had a report of both a serum albumin and total serum bilirubin (TSB) level on the same day between birth and 14 days of life.

RESULTS

There were 382 190 paired albumin and bilirubin levels across 164 401 neonates (15% of the 1 072 682 infants in the clinical data warehouse). Both gestational age and postnatal age were independent factors that influenced the values for serum albumin, TSB, and B/A ratio (ANOVA; P < .0001). TSB and B/A ratios values above birth weight-specific thresholds for exchange transfusions were uncommon (<6% of infants). Hypoalbuminemia (<2.5 mg/dL) was common (29% of infants). Neonates with serum albumin levels <2.5 g/dL or with B/A ratio levels exceeding exchange thresholds were at higher risk of death compared with infants who did not exceed these levels. This association was independent of other risk factors (estimated gestational age, birth weight, sex, and the presence of a major anomaly).

CONCLUSION

Both gestational age and postnatal age influence TSB, albumin, and B/A ratios; hypoalbuminemia and extreme B/A ratios are associated with an increased risk of death.

The Bilirubin Binding Panel: A Henderson-Hasselbalch Approach to Neonatal Hyperbilirubinemia

Poor plasma bilirubin binding increases the risk of bilirubin neurotoxicity in newborns with hyperbilirubinemia. New laboratory tests may soon make it possible to obtain a complete bilirubin binding panel when evaluating these babies. The 3 measured components of the panel are the plasma total bilirubin concentration (B_Total), which is currently used to guide clinical care; the bilirubin binding capacity (BBC); and the concentration of non-albumin bound or free bilirubin (B_Free). The fourth component is the bilirubin-albumin equilibrium dissociation constant, K_D, which is calculated from B_Total, BBC, and B_Free The bilirubin binding panel is comparable to the panel of components used in the Henderson-Hasselbalch approach to acid-base assessment. Bilirubin binding population parameters (not prospective studies to determine whether the new bilirubin binding panel components are better predictors of bilirubin neurotoxicity than B_Total) are needed to expedite the clinical use of bilirubin binding. At any B_Total, the B_Free and the relative risk of bilirubin neurotoxicity increase as the K_D/BBC ratio increases (ie, bilirubin binding worsens). Comparing the K_D/BBC ratio of newborns with B_Total of concern with that typical for the population helps determine whether the risk of bilirubin neurotoxicity varies significantly from the inherent risk at that B_Total Furthermore, the bilirubin binding panel individualizes care because it helps to determine how aggressive intervention should be at any B_Total, irrespective of whether it is above or below established B_Total guidelines. The bilirubin binding panel may reduce anxiety, costs, unnecessary treatment, and the likelihood of undetected bilirubin neurotoxicity.

A Hypothesis for Using Pathway Genetic Load Analysis for Understanding Complex Outcomes in Bilirubin Encephalopathy

Genetic-based susceptibility to bilirubin neurotoxicity and chronic bilirubin encephalopathy (kernicterus) is still poorly understood. Neonatal jaundice affects 60–80% of newborns, and considerable effort goes into preventing this relatively benign condition from escalating into the development of kernicterus making the incidence of this potentially devastating condition very rare in more developed countries. The current understanding of the genetic background of kernicterus is largely comprised of mutations related to alterations of bilirubin production, elimination, or both. Less is known about mutations that may predispose or protect against CNS bilirubin neurotoxicity. The lack of a monogenetic source for this risk of bilirubin neurotoxicity suggests that disease progression is dependent upon an overall decrease in the functionality of one or more essential genetically controlled metabolic pathways. In other words, a “load” is placed on key pathways in the form of multiple genetic variants that combine to create a vulnerable phenotype. The idea of epistatic interactions creating a pathway genetic load (PGL) that affects the response to a specific insult has been previously reported as a PGL score. We hypothesize that the PGL score can be used to investigate whether increased susceptibility to bilirubin-induced CNS damage in neonates is due to a mutational load being placed on key genetic pathways important to the central nervous system's response to bilirubin neurotoxicity. We propose a modification of the PGL score method that replaces the use of a canonical pathway with custom gene lists organized into three tiers with descending levels of evidence combined with the utilization of single nucleotide polymorphism (SNP) causality prediction methods. The PGL score has the potential to explain the genetic background of complex bilirubin induced neurological disorders (BIND) such as kernicterus and could be the key to understanding ranges of outcome severity in complex diseases. We anticipate that this method could be useful for improving the care of jaundiced newborns through its use as an at-risk screen. Importantly, this method would also be useful in uncovering basic knowledge about this and other polygenetic diseases whose genetic source is difficult to discern through traditional means such as a genome-wide association study.

Bilirubin Binding Capacity in the Preterm Neonate

Total serum/plasma bilirubin (TB), the biochemical measure currently used to evaluate and manage hyperbilirubinemia, is not a useful predictor of bilirubin-induced neurotoxicity in premature infants. Altered bilirubin-albumin binding in premature infants limits the usefulness of TB in premature infants. In this article, bilirubin-albumin binding, a modifying factor for bilirubin-induced neurotoxicity, in premature infants is reviewed.

Bilirubin-Induced Neurotoxicity in the Preterm Neonate

Bilirubin-induced neurotoxicity in preterm neonates remains a clinical concern. Multiple cellular and molecular cascades likely underlie bilirubin-induced neuronal injury, including plasma membrane perturbations, excitotoxicity, neuroinflammation, oxidative stress, and cell cycle arrest. Preterm newborns are particularly vulnerable secondary to central nervous system immaturity and concurrent adverse clinical conditions that may potentiate bilirubin toxicity. Acute bilirubin encephalopathy in preterm neonates may be subtle and manifest primarily as recurrent symptomatic apneic events. Low-bilirubin kernicterus continues to be reported in preterm neonates, and although multifactorial in nature, is often associated with marked hypoalbuminemia.

Albumin administration prevents neurological damage and death in a mouse model of severe neonatal hyperbilirubinemia

Therapies to prevent severe neonatal unconjugated hyperbilirubinemia and kernicterus are phototherapy and, in unresponsive cases, exchange transfusion, which has significant morbidity and mortality risks. Neurotoxicity is caused by the fraction of unconjugated bilirubin not bound to albumin (free bilirubin, Bf). Human serum albumin (HSA) administration was suggested to increase plasma bilirubin-binding capacity. However, its clinical use is infrequent due to difficulties to address its potential preventive and curative benefits, and to the absence of reliable markers to monitor bilirubin neurotoxicity risk. We used a genetic mouse model of unconjugated hyperbilirubinemia showing severe neurological impairment and neonatal lethality. We treated mutant pups with repeated HSA administration since birth, without phototherapy application. Daily intraperitoneal HSA administration completely rescued neurological damage and lethality, depending on dosage and administration frequency. Albumin infusion increased plasma bilirubin-binding capacity, mobilizing bilirubin from tissues to plasma. This resulted in reduced plasma Bf, forebrain and cerebellum bilirubin levels. We showed that, in our experimental model, Bf is the best marker to determine the risk of developing neurological damage. These results support the potential use of albumin administration in severe acute hyperbilirubinemia conditions to prevent or treat bilirubin neurotoxicity in situations in which exchange transfusion may be required.

The Ages and Stages Questionnaire and Neurodevelopmental Impairment in Two-Year-Old Preterm-Born Children

Objective

To test the ability of the Ages and Stages Questionnaire, Third Edition (ASQ3) to help identify or exclude neurodevelopmental impairment (NDI) in very preterm-born children at the corrected age of two.

Methods

We studied the test results of 224 children, born at <32 postmenstrual weeks, who had scores on ASQ3 and Bayley Scales of Infant and Toddler Development, Third Edition (BSIDIII) and neurological examination at 22–26 months’ corrected age. We defined NDI as a score of <70 on the cognitive—or motor composite scale of BSIDIII, or impairment on neurological examination or audiovisual screening. We compared NDI with abnormal ASQ3 scores, i.e., < -2SDs on any domain, and with ASQ3 total scores. To correct for possible overestimation of BSIDIII, we also analyzed the adjusted BSIDIII thresholds for NDI, i.e., scores <80 and <85.

Results

We found 61 (27%) children with abnormal ASQ3 scores, and 10 (4.5%) children who had NDI with original BSIDIII thresholds (<70). Twelve children had NDI at BSIDIII thresholds at <80, and 15 had <85. None of the 163 (73%) children who passed ASQ3 had NDI. The sensitivity of ASQ3 to detect NDI was excellent (100%), its specificity was acceptable (76%), and its negative predictive value (NPV) was 100%. Sensitivity and NPV remained high with the adjusted BSIDIII thresholds.

Conclusion

The Ages and Stages Questionnaire is a simple, valid and cost-effective screening tool to help identify and exclude NDI in very preterm-born children at the corrected age of two years.

Movement disorders due to bilirubin toxicity

Advances in the care of neonatal hyperbilirubinemia have led to a decreased incidence of kernicterus. However, neonatal exposure to high levels of bilirubin continues to cause severe motor symptoms and cerebral palsy (CP). Exposure to moderate levels of unconjugated bilirubin may also cause damage to the developing central nervous system, specifically the basal ganglia and cerebellum. Brain lesions identified using magnetic resonance imaging following extreme hyperbilirubinemia have been linked to dyskinetic CP. Newer imaging techniques, such as diffusion tensor imaging or single-photon emission computed tomography, allow quantification of more subtle white matter injury following presumed exposure to unbound bilirubin, and may explain more subtle movement disorders. New categories of bilirubin-induced neurologic dysfunction, characterized by subtle bilirubin encephalopathy following moderate hyperbilirubinemia, have been implicated in long-term motor function. Further research is needed to identify subtle impairments resulting from moderate-severe neonatal hyperbilirubinemia, to understand the influence of perinatal risk factors on bilirubin toxicity, and to develop neuroprotective treatment strategies to prevent movement disorders due to bilirubin toxicity.

The enigma of low bilirubin kernicterus in premature infants: why does it still occur, and is it preventable?

Low bilirubin kernicterus in preterm neonates, though rare, remains an unpredictable and refractory form of brain injury. Hypoalbuminemia, co-morbid CNS insult(s), infection, and inflammation are contributing causes that, in many cases, appear to interact in potentiating bilirubin neurotoxicity. Despite compulsive attention to serum bilirubin levels, and clinical and laboratory indices of neurotoxicity risk, low bilirubin kernicterus continues to be seen in contemporary NICUs. While efforts to refine and improve current treatment guidelines are certainly needed, such revision(s) will also have to take into account the risks and benefits of any intervention, including phototherapy.

Bilirubin-albumin binding, bilirubin/albumin ratios, and free bilirubin levels: where do we stand?

Treatment for unconjugated hyperbilirubinemia is predominantly based on one parameter, i.e., total serum bilirubin (TSB) levels. Yet, overt kernicterus has been reported in preterm infants at relatively low TSB levels, and it has been repeatedly shown that free unconjugated bilirubin (freeUCB) levels, or bilirubin/albumin (B/A) ratios for that matter, are more closely associated with bilirubin neurotoxicity. In this article, we review bilirubin-albumin binding, UCBfree levels, and B/A ratios in addition to TSB levels to individualize and optimize treatment especially in preterm infants. Methods to measure bilirubin-albumin binding or UCBfree are neither routinely performed in Western clinical laboratories nor incorporated in current management guidelines on unconjugated hyperbilirubinemia. For bilirubin-albumin binding, this seems justified because several of these methods have been challenged, and sufficiently powered prospective trials on the clinical benefits are lacking. Technological advances in the measurement of UCBfree may provide a convenient means for integrating UCBfree measurements into routine clinical management of jaundiced infants. A point-of-care method, as well as determination of UCBfree levels in various newborn populations, is desirable to learn more about variations in time and how various clinical pathophysiological conditions affect UCBfree levels. This will improve the estimation of approximate UCBfree levels associated with neurotoxicity. To delineate the role of UCBfree in the management of jaundiced (preterm) infants, trials are needed using UCBfree as treatment parameter. The additional use of the B/A ratio in jaundiced preterms has been evaluated in the Bilirubin Albumin Ratio Trial (BARTrial; Clinical Trials: ISRCTN74465643) but failed to demonstrate better neurodevelopmental outcome in preterm infants <32 weeks assigned to the study group. Awaiting a study in which infants are assigned to be managed solely on the basis of their B/A ratio (with TSB excluded ) versus TSB levels alone-and determining which group does better-the additional use of the B/A ratio in the management of hyperbilirubinemia in preterms is not advised. In conjunction with TSB levels, other parameters possibly allow for more accurate prediction of bilirubin toxicity. Yet, different methodologies for estimating these parameters exist, and sufficiently powered, prospective clinical trials supporting their clinical benefit, i.e., reduced bilirubin neurotoxicity when using these parameters, are lacking. Their use in addition to TSB needs to be prospectively evaluated, especially in preterm neonates, and preferentially in randomized clinical trials, which include specific risk factors and assessment of clinical relevant outcome measures for detecting those infants at risk of bilirubin toxicity.

Serum bilirubin and bilirubin/albumin ratio as predictors of bilirubin encephalopathy

BACKGROUND AND OBJECTIVE

Bilirubin/albumin ratio (B/A) may provide a better estimate of free bilirubin than total serum bilirubin (TSB), thus improving identification of newborns at risk for bilirubin encephalopathy. The objective of the study was to identify thresholds and compare specificities of TSB and B/A in detecting patients with acute and posttreatment auditory and neurologic impairment.

METHODS

A total of 193 term/near-term infants, admitted for severe jaundice to Cairo University Children's Hospital, were evaluated for neurologic status and auditory impairment (automated auditory brainstem response), both at admission and posttreatment by investigators blinded to laboratory results. The relationships of TSB and B/A to advancing stages of neurotoxicity were compared by using receiver operating characteristic curves.

RESULTS

TSB and B/A ranged from 17 to 61 mg/dL and 5.4 to 21.0 mg/g, respectively; 58 (30%) of 193 subjects developed acute bilirubin encephalopathy, leading to kernicterus in 35 infants (13 lethal). Auditory impairment was identified in 86 (49%) of 173 infants at admission and in 22 of 128 at follow-up. In the absence of clinical risk factors, no residual neurologic or hearing impairment occurred unless TSB exceeded 31 mg/dl. However, transient auditory impairment occurred at lower TSB and B/A (22.9 mg/dL and 5.7 mg/g, respectively). Intervention values of TSB and B/A set at high sensitivity to detect different stages of neurotoxicity had nearly the same specificity.

CONCLUSIONS

Both TSB and B/A are strong predictors of neurotoxicity, but B/A does not improve prediction over TSB alone. Threshold values detecting all affected patients (100% sensitivity) increase with advancing severity of neurotoxicity.