Lois Johnson

Predictive ability of a predischarge hour-specific serum bilirubin for subsequent significant hyperbilirubinemia in healthy term and near-term newborns

Objective. To assess the predictive ability of a universal predischarge serum bilirubin measurement to screen for risk of subsequent significant hyperbilirubinemia in the direct Coombs negative healthy term and near-term newborn during the first postnatal week. Methods. Total serum bilirubin (TSB) levels were obtained at the time of the routine metabolic screen in all term and near-term newborns cared for in the Pennsylvania Hospital Well Baby Nursery (n = 13 003). Postnatal age (in hours) at the time of TSB measurement was recorded. A percentile-based bilirubin nomogram for the first week was constructed from hour-specific predischarge and postdischarge TSB values of newborns (n = 2840; median BW = 3230 g and median gestational age = 39 weeks) who met classification criteria for healthy newborns (excluding those with a positive direct Coombs test or those requiring phototherapy before age 60 hours) and who were enrolled in a hospital supervised home or outpatient follow-up program. The accuracy of the predischarge TSB as a predictor of subsequent degree of hyperbilirubinemia was determined. Results. The study patients in the nomogram were racially diverse. Nearly 60% were breastfed. Predischarge, 6.1% of the study population (172/2840) had TSB values in the high-risk zone (≥95th percentile) at 18 to 72 hours; of these, 39.5% (68/172) remained in that zone (likelihood ratio [LR] = 14.08, sensitivity = 54%; specificity = 96.2%, probability = 39.5%). Predischarge, 32.1% of the population (912/2840) had TSB values in the intermediate-risk zone. In a clinically significant minority of these newborns (58/912 or 6.4%), the postdischarge TSB moved into the high-risk zone (LR of this move: 3.2 from the upper-intermediate zone and .48 from the lower-intermediate risk zone). The predischarge TSB in 61.8% of the newborns (1756/2840) was in the low-risk zone (<40th percentile) and there was no measurable risk for significant hyperbilirubinemia (LR = 0, sensitivity = 100%; specificity = 64.7%; probability = 0%). Conclusions. An hour-specific TSB before hospital discharge can predict which newborn is at high, intermediate or low risk for developing clinically significant hyperbilirubinemia (specifically defined as TSB levels ≥95th percentile for age in hours). Risk designation and subsequent increases or decreases of in TSB can be easily monitored on an hour-specific percentile based predictive bilirubin nomogram. A predischarge TSB measured as a universal policy would facilitate targeted intervention and follow-up in a safe, cost-effective manner. In conjunction with bilirubin practice parameter of the American Academy of Pediatrics, it could reduce the potential risk for bilirubin-induced neurologic dysfunction.

Noninvasive measurement of total serum bilirubin in a multiracial predischarge newborn population to assess the risk of severe hyperbilirubinemia.

Background. Jaundice in near-term and term newborns is a frequent diagnosis that may prompt hospital readmission in the first postnatal week. Hyperbilirubinemia, when excessive, can lead to potentially irreversible bilirubin-induced neurotoxicity. Predischarge risk assessment (at 24–72 hours of age) for subsequent excessive hyperbilirubinemia is feasible by a laboratory-based assay of total serum bilirubin (TSB). Hypothesis. Noninvasive, transcutaneous, point-of-care measurement of transcutaneous bilirubin (TcB) predischarge by multiwavelength spectral analysis, using a portable BiliCheck device (SpectRx Inc, Norcross, GA), is clinically equivalent to measurement of TSB in a diverse, multiracial term and near-term newborn population and predictive of subsequent hyperbilirubinemia. Methodology. We evaluated a hand-held device that uses multiwavelength spectral reflectance analysis to measure TcB (BiliCheck). The study population (490 term and near-term newborns) was racially diverse (59.1% white, 29.5% black, 3.46% Hispanic, 4.48% Asian, and 3.46% other) and was evaluated at 2 separate institutions using multiple (11) devices. The postnatal age ranged from 12 to 98 hours and the ranges of birth weights and gestational ages were 2000 to 5665 g and 35 to 42 weeks, respectively. All transcutaneous evaluations were performed contemporaneously and paired with a heelstick TSB measurement. All TSB assays were performed by high performance liquid chromatography, as well as by diazo dichlorophenyldiazonium tetrafluoroborate techniques. Results. TSB values ranged from .2 to 18.2 mg/dL (mean ± standard deviation: 7.65 ± 3.35 mg/dL). The overall correlation of TSB (by high performance liquid chromatography technique) to TcB (by BiliCheck devices) was linear and statistically significant (r = .91;r 2 = .83; TcB = .84; TSB = +.75; standard error of regression line = 1.38; P< .001; n = 490 infants; 1788 samples). Similar regression statistics were evident in subset populations categorized by race (white: r = .91 [n = 289 infants]; black: r = .91 [n = 145 infants]) as well as by gestation (term: r = .91 [n = 1625 samples]; near-term:r = .89 [n = 163 samples]). Intradevice precision was determined to be .59 mg/dL (2–3 measurements per infant with 1 device; n = 210 infants; 510 samples in a separate subset). Interdevice evaluation of 11 devices determined the precision to be .68 mg/dL (2–4 devices used for measurements per patient). In 23 of 419 of the study population infants who were in the 24- to 72-hour age range, the predischarge TSB values designated them to be at high risk for subsequent excessive hyperbilirubinemia (above the 95th percentile track on the hour-specific bilirubin nomogram). For these infants, the paired BiliCheck TcB values were all above the 75th percentile track (negative predictive value = 100%; positive predictive value = 32.86%; sensitivity = 100%; specificity = 88.1%; likelihood ratio = 8.43). Conclusions. Our data demonstrate the accuracy and reproducibility of the predischarge BiliCheck measurements in term and near-term newborn infants of diverse races and ethnicities. Infants with predischarge BiliCheck values above the 75th percentile of hour-specific TSB values on the bilirubin nomogram may be considered to be at high risk for subsequent excessive hyperbilirubinemia. Further studies are needed to assess the efficacy of this technique in preterm infants, those undergoing phototherapy, and those with TSB values of ≥15 mg/dL (≥256 μmol/L).

Clinical report from the pilot USA Kernicterus Registry (1992 to 2004)

To identify antecedent clinical and health services events in infants (⩾35 weeks gestational age (GA)) who were discharged as healthy from their place of birth and subsequently sustained kernicterus. We conducted a root-cause analysis of a convenience sample of 125 infants ⩾35 weeks GA cared for in US healthcare facilities (including off-shore US military bases). These cases were voluntarily reported to the Pilot USA Kernicterus Registry (1992 to 2004) and met the eligibility criteria of acute bilirubin encephalopathy (ABE) and/or post-icteric sequelae. Multiple providers at multiple sites managed this cohort of infants for their newborn jaundice and progressive hyperbilirubinemia. Clinical signs of ABE, verbalized by parents, were often inadequately elicited or recorded and often not recognized as an emergency. Clinical signs of ABE were reported in 7 of 125 infants with a subsequent diagnosis of kernicterus who were not re-evaluated or treated for hyperbilirubinemia, although jaundice was noted at outpatient visits. The remaining infants (n=118) had total serum bilirubin (TSB) levels >20 mg per 100 ml (342 μmol l−1; range: 20.7 to 59.9 mg per 100 ml). No specific TSB threshold coincided with onset of ABE. Of infants <37 weeks GA with kernicterus, 34.9% were LGA (large for gestational age) as compared with 24.7% of term infants (>37 weeks GA). Although >90% mothers initiated breast-feeding, assessment of milk transfer and lactation support was suboptimal in most. Mortality was 4% (5 of 125) in infants readmitted at age ⩽1 week. Along with a rapid rise of TSB (>0.2 mg per 100 ml per hour), contributing factors, alone or in combination, included undiagnosed hemolytic disease, excessive bilirubin production related to extra-vascular hemolysis and delayed bilirubin elimination (including increased enterohepatic circulation, diagnosed and undiagnosed genetic disorders) in the context of known late prematurity (<37 weeks), glucose 6-phosphate-dehydrogenase deficiency, infection and dehydration. Readmission was at age ⩽5 days in 81 of 118 (69%) infants and <10 days in 101 of 118 (86%) infants. TSB levels were ⩽35 mg per 100 ml (598 μmol l−1) in 46 (39%) infants, of whom one died before exchange transfusion, one was untreated and one was lost to follow-up. Timely and efficacious bilirubin reduction interventions defined by ‘crash-cart’ initiation of immediate intensive phototherapy and urgent exchange transfusion were accomplished in 11 of 43 infants, which were compared with 12 of 43 infants in whom a timely exchange sometimes could not be accomplished. No overt sequelae were found in 8 of 11 infants (73%) treated with a ‘crash-cart’ approach compared with none without sequelae when exchange was delayed by pre-admission delays, technical factors or need to transfer to a tertiary facility. None of the remaining 20 of 43 infants treated only with phototherapy escaped sequelae. Regardless of age at readmission and intervention, infants with peak measured TSB >35 mg per 100 ml had post-icteric sequelae (n=73). There was a narrow margin of safety between birthing hospital discharge or home birth and readmission to a tertiary neonatal/pediatric facility. Progression of hyperbilirubinemia to hazardous levels and onset of neurological signs were often not identified as infants care and medical supervision transitioned during the first week after birth. The major underlying root cause for kernicterus was systems failure of services by multiple providers at multiple sites and inability to identify the at-risk infant and manage severe hyperbilirubinemia in a timely manner.

Toward Understanding Kernicterus: A Challenge to Improve the Management of Jaundiced Newborns

PURPOSE. We sought to evaluate the sensitivity and specificity of total serum bilirubin concentration (TSB) and free (unbound) bilirubin concentration (Bf) as predictors of risk for bilirubin toxicity and kernicterus and to examine consistency between these findings and proposed mechanisms of bilirubin transport and brain uptake. METHODS. A review of literature was undertaken to define basic principles of bilirubin transport and brain uptake leading to neurotoxicity. We then reviewed experimental and clinical evidence that relate TSB or Bf to risk for bilirubin toxicity and kernicterus. RESULTS. There are insufficient published data to precisely define sensitivity and specificity of either TSB or Bf in determining risk for acute bilirubin neurotoxicity or chronic sequelae (kernicterus). However, available laboratory and clinical evidence indicate that Bf is better than TSB in discriminating risk for bilirubin toxicity in patients with severe hyperbilirubinemia. These findings are consistent with basic pharmacokinetic principles involved in bilirubin transport and tissue uptake. CONCLUSIONS. Experimental and clinical data strongly suggest that measurement of Bf in newborns with hyperbilirubinemia will improve risk assessment for neurotoxicity, which emphasizes the need for additional clinical evaluation relating Bf and TSB to acute bilirubin toxicity and long-term outcome. We speculate that establishing risk thresholds for neurotoxicity by using newer methods for measuring Bf in minimally diluted serum samples will improve the sensitivity and specificity of serum indicators for treating hyperbilirubinemia, thus reducing unnecessary aggressive intervention and associated cost and morbidity.

Kernicterus: Epidemiological Strategies for Its Prevention through Systems-Based Approaches

Kernicterus, thought to be due to severe hyperbilirubinemia, is an uncommon disorder with tragic consequences, especially when it affects healthy term and near-term infants. Early identification, prevention and treatment of severe hyperbilirubinemia should make kernicterus a preventable disease. However, national epidemiologic data are needed to monitor any preventive strategies. Recommendations are provided to obtain prospective data on the prevalence and incidence of severe hyperbilirubinemia and associate mortality and neurologic injury using standardized definitions, explore the clinical characteristics and root causes of kernicterus in children identified in the Kernicterus Pilot Registry, identify and test an indicator for population surveillance, validating systems-based approaches to the management of newborn jaundice, and explore the feasibility of using biologic or genetic markers to identify infants at risk for hyperbilirubinemia. Increased knowledge about the incidence and consequences of severe hyperbilirubinemia is essential to the planning, implementation and assessment of interventions to ensure that infants discharged as healthy from their birth hospitals have a safer transition to home, avoiding morbidity due to hyperbilirubinemia and other disorders.At a recent NIHCD-sponsored conference, key questions were raised about kernicterus and the need for additional strategies for its prevention. These questions and an approach to their answers form the basis of this report.

Effect of sustained pharmacologic vitamin E levels on incidence and severity of retinopathy of prematurity: A controlled clinical trial

The incidence and severity of retinopathy of prematurity (ROP) as affected by vitamin E prophylaxis at pharmacologic serum levels (5 mg/dl) were evaluated in a double-masked clinical trial of infants with a birth weight less than or equal to 2000 gm or a gestational age less than or equal to 36 weeks. The infants were enrolled by age 5 days and randomly assigned to receive parenterally administered, and later orally administered, free alpha-tocopherol (vitamin E) or its placebo. Study medication was continued until retinal vascularization was complete or active ROP had subsided, except in infants with a diagnosis of severe disease, in whom vitamin E was substituted for study medication. Acute ROP data were collected on 755 infants. Logistic regression analysis, with control for immaturity, oxygen exposure, and other illness risk factors, showed a decrease in incidence of ROP in vitamin E-treated infants (p = 0.003, all infants; p = 0.035, infants weighing less than or equal to 1500 gm at birth). Among the 424 infants weighing less than or equal to 1500 gm at birth, the age at enrollment influenced treatment effect (age day 0 to 1, p = 0.006 (n = 288) vs age day 2 to 5, p greater than 0.1 (n = 136]. Overall, 77.6% of infants with ROP had mild disease. Moderate to severe ROP was confined to infants weighing greater than or equal to 1500 gm at birth (25 given placebo, 25 given vitamin E), with progression to severe disease in nine placebo-treated versus three vitamin E-treated infants (p = 0.048). The incidence of severe ROP per se was not significantly decreased (all birth weights, p = 0.086; less than or equal to 1500 gm birth weight, p = 0.080); the sample size was too small, however, to assess this end point adequately. An increased incidence of sepsis and late-onset necrotizing enterocolitis was found among vitamin E-treated infants weighing less than or equal to 1500 gm at birth who received study medication for greater than or equal to 8 days (p = 0.006). Because most ROP is mild in degree and regresses completely, the risk/benefit ratio of pharmacologic prophylaxis for ROP is unfavorable. Treatment of moderate and severe ROP with vitamin E above physiologic serum levels (greater than 3 mg/dl) appears promising and should be further investigated. The interpretation of cicatricial outcome was confounded by the small number of patients involved and by subsequent treatment of severe ROP in placebo-treated infants with vitamin E.

The clinical syndrome of bilirubin-induced neurologic dysfunction.

We believe that the syndrome of bilirubin-induced neurologic dysfunction [BIND] represents a spectrum of neurologic manifestations among vulnerable infants who have experienced an exposure to bilirubin of lesser degree than generally described in previous publications. Clinical neuro-motor manifestations extend to a range of subtle processing disorders with objective disturbances of visual-motor, auditory, speech, cognition, and language among infants with a previous history of moderate-to-severe hyperbilirubinemia of varied duration. Confounding effects include prematurity, hemolysis, perinatal-neonatal complications, altered bilirubin-albumin binding, severity and duration of bilirubin exposure, and the individual vulnerability of the infant related to genetic, family, social, and educational predilection, regardless of the cause of neonatal jaundice. Tools to better assess BIND specific domains of multisensory processing disorders, identified by pyschometric, audiologic, speech, language and visual-motor, and neuromotor examination would allow for prospective surveillance of infants at risk for the syndrome.

Vitamin E and Retinopathy of Prematurity: Follow-up at One Year

Five hundred forty-five infants weighing less than 1501 g at birth were entered into a randomized, prospective study to determine the effect of high serum levels (5 mg/dL) of vitamin E used prophylactically to try to prevent or alter the natural course of retinopathy of prematurity (ROP) and its sequel, retrolental fibroplasia (RLF). Three hundred twenty-eight infants were available for the one- to two-year eye examination. Although there was a trend (P = 0.072) toward less severe RLF among vitamin E-treated infants, the incidence of RLF was 11/162 (6.8%) in the placebo treated (P) infants, and 12/166 (7.2%) in the vitamin E-treated (E) infants. The incidences of hyperopia, myopia, anisometropia, strabismus and amblyopia were also similar in both the P and E groups.

Mitochondrial abnormalities in bilirubin encephalopathy.

Mitochondria in neurons of Gunn rats with bilirubin encephalopathy are enlarged and contain vesicles filled with glycogen-like granules. This study demonstrates that bilirubin exerts at least some of its toxic effects by damaging mitochondria, but it appears unlikely that oxidative phosphorylation and depression of respiration are the primary effects of bilirubin on neurons in vivo, alternative mechanisms of bilirubin toxicity in vivo are discussed.

Clinical signs and morphologic abnormalities in Gunn rats treated with sulfadimethoxine

Gunn rats treated with sulfadimethoxine between 18 hours after birth and 33 days of age developed acute neurologic signs and increased yellow staining of their brains. In animals treated between the ages of 4 and 22 days, the neurologic abnormalities were proportional to the serum bilirubin levels. Animals treated from 18 to 48 hours after birth develop more severe signs than older animals with similar bilirubin levels, and those older than 22 days develop mild but definite neurologic signs. This study confirms the importance of the albumin binding of bilirubin as a protective factor in hyperbilirubinemia. We conclude that it is superfluous to postulate a blood-brain barrier to bilirubin to explain kernicterus, and that anoxia is not essential for its development. Bilirubin has access to the central nervous system beyond the newborn period. The reasons for the extreme toxicity of sulfonamides to Gunn rats in the first 2 days of life and the relatively mild effects in animals treated at 28 and 33 days are discussed. It is suggested that the characteristic pattern of yellow discoloration of the brain in kernicterus could be largely accounted for by differences in regional cerebral blood flow.