Maximum Total Serum Bilirubin Research Articles

The spectrum of ABO haemolytic disease of the fetus and newborn in neonates born to group O mothers.

ABO haemolytic disease of the fetus and newborn (HDFN) is a lesser recognized entity; however, the severity may vary in neonates. This prospective observational study was performed to determine the severity and risk of ABO-HDFN in neonates born to O group mothers. A total of 260 neonates born to non-alloimmunized blood group O mothers were recruited. Blood group O neonates were excluded from the study. Neonatal direct antiglobulin test (DAT) was performed using the column agglutination technique. They were monitored for clinical and laboratory parameters and followed up at 6-8 weeks. The maternal anti-A and anti-B titres (IgM and IgG) were also done. A total of 176 neonates with blood group A (77/260; 29.6%) and B (99/260; 38.1%) were finally included in the study, and 15 (8.5%) of them were DAT positive. Overall, 26.7% (47/176) neonates received phototherapy, 172 (97.7%) survived and none required readmission. The median (inter-quartile range [IQR]) maternal IgG anti-B titre (32 [32-64]) was significantly higher (p < 0.001) than the IgG anti-A titre (16 [8-64]). The maximum total serum bilirubin in neonates had a significant positive association with neonatal birth weight (p=0.045), positive DAT (p=0.006) and requirement of phototherapy (p < 0.001). The relative risk (95% CI) of a DAT-positive neonate requiring phototherapy was 4.55 (3.12-6.33). The frequency of ABO incompatibility in neonates born to group O mothers was 67.69% (176/260). The maternal IgG titre of ≥64 could be a good predictor for identifying the neonates at risk of developing hyperbilirubinaemia requiring phototherapy.

Evaluation of Rh-Hemolytic Disease in Neonates and Management with Early Intensive Phototherapy in the Neonatal Intensive Care Unit.

In neonates with Rh-hemolytic disease, light emitting diode (LED) phototherapy allows delivery of high spectral irradiance (SI). A linear correlation exists between SI and efficacy of phototherapy with no saturation point. There is scant data on evaluation and early phototherapy using LED units in Rh-hemolytic disease. This study aimed to describe the hemoglobin (Hb), hematocrit (Hct), total serum bilirubin (TSB), phototherapy parameters and short-term outcomes in neonates with Rh-hemolytic disease. Maternal parameters for Rh-isoimmunization were recorded and monitoring of fetal anemia by Doppler ultrasound was done. Early intensive phototherapy within 1 h of birth was initiated for cord blood Hb below 13.6 g/dl and/or TSB greater than 2.8 mg/dl. Fifty Rh positive neonates were enrolled of which 11/50 (22%) received intrauterine transfusions. The maximum TSB remained below 18 mg/dl in 42/50 (84%) of neonates. The mean SI on the trunk was 56.260 ± 8.768 µW/cm2/nm and duration of phototherapy was 7 ± 3.29 days (mean ± SD). There was a positive correlation between strength of indirect antiglobulin test and cord blood Hb: correlation coefficient (r) = 0.295; direct antiglobulin test and duration of phototherapy: r = 0.331. Early packed red blood cell (PRBC) transfusion was required in 8/50 (16%) neonates while 20/50 (40%) required late transfusions. With a mean SI of 56.260 ± 8.768 µW/cm2/nm on the trunk, TSB remained below 18 mg/dl in majority thereby avoiding exchange transfusion. Early or late PRBC transfusion requirement was 1 (1-2) (median ± interquartile range).

Hyperbilirubinemia, Phototherapy, and Childhood Asthma.

Our aim was to quantify the associations of both hyperbilirubinemia and phototherapy with childhood asthma using a population-based cohort with total serum bilirubin (TSB) levels. Retrospective cohort study of infants born at ≥35 weeks' gestation in the Kaiser Permanente Northern California health system (n = 109 212) from 2010 to 2014. Cox models were used to estimate hazard ratios (HRs) for a diagnosis of asthma. In the study, 16.7% of infants had a maximum TSB level of ≥15 mg/dL, 4.5% of infants had a maximum TSB level of ≥18 mg/dL, and 11.5% of infants received phototherapy. Compared with children with a maximum TSB level of 3 to 5.9 mg/L, children with a TSB level of 9 to 11.9 mg/dL, 12 to 14.9 mg/dL, and 15 to 17.9 mg/dL were at an increased risk for asthma (HR: 1.22 [95% confidence interval (CI): 1.11-1.3], HR: 1.18 [95% CI: 1.08-1.29], and HR: 1.30 [95% CI: 1.18-1.43], respectively). Children with a TSB level of ≥18 mg/dL were not at an increased risk for asthma (HR: 1.04; 95% CI: 0.90-1.20). In propensity-adjusted analyses, phototherapy was not associated with asthma (HR: 1.07; 95% CI: 0.96-1.20). Modest levels of hyperbilirubinemia were associated with an increased risk of asthma, but an association was not seen at higher levels. No dose-response relationship was seen. Using phototherapy to prevent infants from reaching these modest TSB levels is unlikely to be protective against asthma.

Extreme neonatal hyperbilirubinemia, acute bilirubin encephalopathy, and kernicterus spectrum disorder in children with galactosemia.

Galactosemia has not been recognized as a cause of extreme neonatal hyperbilirubinemia, although growing evidence supports this association. In a retrospective cohort study, we identified children with galactosemia due to GALT deficiency using the Danish Metabolic Laboratory Database. Among these, we identified children with extreme neonatal hyperbilirubinemia or symptoms of ABE. Extreme neonatal hyperbilirubinemia was defined as maximum total serum bilirubin (TSBmax)) level ≥450 µmol/L and a ratio of conjugated serum bilirubin/TSB <0.30. We identified 21 children with galactosemia (incidence:1:48,000). Seven children developed extreme neonatal hyperbilirubinemia (median [range] TSBmax level: 491 [456-756] µmol/L), accounting for 1.7% of all extreme neonatal hyperbilirubinemia cases. During the first 10 days of life, hyperbilirubinemia was predominantly of unconjugated type. Four children developed symptoms of intermediate/advanced ABE. One additional child had symptoms of intermediate/advanced ABE without having extreme neonatal hyperbilirubinemia. On follow-up, one child had KSD. Galactosemia is a potential cause of extreme neonatal hyperbilirubinemia, ABE, and KSD. It is crucial that putative galactosemic children are treated aggressively with phototherapy to prevent ABE and KSD. Thus it is important that galactosemia is part of the work up for unconjugated hyperbilirubinemia.

Association Between Laboratory Calibration of a Serum Bilirubin Assay, Neonatal Bilirubin Levels, and Phototherapy Use.

The American Academy of Pediatrics treatment recommendations for neonatal jaundice are based on age-specific total serum bilirubin (TSB) levels. In May 2012, Ortho Clinical Diagnostics adjusted the calibrator values for Vitros Chemistry Products BuBc Slides (Ortho Clinical Diagnostics), a widely used method to quantify TSB, after concerns of positively biased results. To investigate the association between recalibration of a reflectance spectrophotometry serum bilirubin assay and TSB levels and phototherapy use among newborns. Descriptive study comparing TSB levels and phototherapy use before and after recalibration at Kaiser Permanente Northern California, a large, integrated health care delivery system. The study evaluated live births at or after 35 weeks' gestation at 12 facilities that used universal serum bilirubin screening before (January 1, 2010, through April 30, 2012; n = 61 677) and after (July 1, 2012, through December 31, 2013; n = 42 571) recalibration. The analysis took place in December 2015. Recalibration of bilirubin testing instruments. Proportions of newborns with (1) at least 1 TSB value at or above 15 mg/dL; (2) at least 1 TSB level exceeding the American Academy of Pediatrics phototherapy threshold; (3) phototherapy during the birth hospitalization; and (4) at least 1 readmission for phototherapy. In 104 420 infants (61 677 in the prerecalibration period and 42 511 in the postrecalibration period), a TSB was obtained in 99.2% of infants during birth and in 99.5% of infants within the first 30 days after birth. The postrecalibration period was associated with a 1.25 mg/dL (95% CI, 1.19-1.31; P < .001) decrease in mean maximum TSB, which led to a 39% relative reduction (from 20.4% to 12.4%) in infants with a TSB level of 15 mg/dL or more and a 51% relative reduction (from 9.3% to 4.5%) in infants with a TSB level that was at or above the American Academy of Pediatrics phototherapy threshold. Phototherapy during birth hospitalizations was reduced by 59% (absolute risk reduction, 5.5%; 95% CI, 4.7%-6.1%) and readmissions for phototherapy by 53% (absolute risk reduction, 1.8%; 95% CI, 1.4%-2.3%). Modest recalibration-induced reductions in mean TSB concentrations was associated with a significant reduction in the percentage of infants with clinically significant hyperbilirubinemia. Current laboratory accuracy standards are insufficient to detect biases that can have significant clinical effect. These data underline the need for increased integration of laboratory expertise into clinical guidelines and to support international initiatives to standardize laboratory measurements.

Complications of Exchange Transfusion in Hospitalized Neonates in Two Neonatal Centers in Hamadan, A Five-Year Experience

Background: Exchange transfusion is commonly used in newborns for immediate treatment of severe hyperbilirubinemia to prevent bilirubin encephalopathy and kernicterus. Objectives: This study aimed to determine etiology and complications in newborns who received exchange transfusion for severe hyperbilirubinemia over the last five years. Patients and Methods: A retrospective study was performed on 28 days old infants who received exchange transfusion due to severe hyperbilirubinemia for a period of five years (from October 1st, 2006 through September 30th, 2011) in two neonatal units at Besat and Fatemieh hospitals in Hamadan, Iran. All data about patients’ demographic characteristics, causes of hyperbilirubinemia, frequency, and complications of exchange transfusion were collected from medical records and analyzed using SPSS Version 12.0). Results: Exchange transfusion was performed in 148 neonates. Eighteen patients (12.2%) received exchange transfusion twice and seventeen patients (11.4%) three times or more. Among 118 neonates 80 (54.9%) were female and the mean gestational age and birth weight were 37.2 ± 2.5 weeks and 2847 ± 699 grams, respectively. The mean maximum total serum bilirubin levels were 27. 7.6 ± 7.28 mg/dL. Hemolytic disease was found in 72 (48.6%) of newborns. The most common cause of hemolysis was ABO incompatibility in 54 (36.5%). The etiologic factors were unidentified in 61 (41.2%) neonates. Complications occurred in 57 (38.5%) neonates and the most common complications were thrombocytopenia in 26 (17.6%) and hypocalcaemia in 17 (11.5%) neonates. Mortality was found in one (0.7%) neonate. Conclusions: The etiology of exchange transfusion was unidentified in most cases; however, ABO incompatibility was the most prevalent cause of hyperbilirubinemia. Complications were common after exchange transfusion and should be considered carefully.

Neonatal Bilirubin Levels and Childhood Asthma in the US Collaborative Perinatal Project, 1959–1965

Evidence shows that asthma originates in early life. Studies have found that phototherapy and/or neonatal jaundice may be associated with asthma. We investigated the association between neonatal bilirubin levels and childhood asthma without phototherapy intervention in the Collaborative Perinatal Project, a multicenter prospective cohort study conducted in the United States from 1959 to 1965. A total of 54,795 livebirths were included, and 40,063 children were followed up until 7 years of age or older. Total serum bilirubin (TSB) levels were examined at 48 hours postpartum in newborns with birthweights of 2,250 g or more. Information on asthma and other diseases through age 7 years was summarized and confirmed by a group of pediatricians and child neurologists. Among 28,807 term infants, the overall prevalence of asthma was 5.26%. Risks of asthma increased with both maximum TSB levels and TSB levels at 48 hours postpartum (P for trend < 0.01). Neonatal maximum TSB levels greater than 15 mg/dL were associated with a 61% increase in the risk of childhood asthma (odds ratio = 1.61, 95% confidence interval: 1.04, 2.08) after adjustment for confounders. In this prospective cohort study of infants born at a time when phototherapy was unavailable, neonatal hyperbilirubinemia was associated with an increased risk of childhood asthma.

Severe Neonatal Hyperbilirubinemia in the Netherlands

Background: The occurrence of severe neonatal hyperbilirubinemia (SH) is partly attributed to nonhospitalized perinatal care. The Netherlands have a high frequency of home births and nonhospitalized perinatal care, and the incidence of SH is unknown. Objective: To assess the effects of home births and early hospital discharge on the incidence of SH in term-born infants in the Netherlands. Methods: In this nationwide prospective surveillance study between 2005 and 2009, infants (≥37 weeks GA) were included if total serum bilirubin (TSB) was ≥500 µmol/l or if they received an exchange transfusion when TSB was ≥340 µmol/l. Results: Seventy-one infants had SH (incidence 10.4/100,000); 43 had a TSB ≥500 μmol/l (incidence 6.3/100,000) and 45 (63%) underwent an exchange transfusion. 26% of the infants with SH were born at home, which is similar to 22% of all term infants who are born at home in the Netherlands (p = 0.41). Maximum TSB levels were similar in infants born at home (523 ± 114 μmol/l) and infants born in hospital (510 ± 123 μmol/l; p = 0.70). Of the 51 infants born in hospital, 33 were discharged and readmitted with SH, with maximal TSB levels (567 ± 114 μmol/l), which were higher than in infants who remained hospitalized (406 ± 47 μmol/l; p = 0.0001). Conclusion: The incidence of severe hyperbilirubinemia in term-born infants in the Netherlands is 10.4 per 100,000, which is similar to other developed countries. Home birth and early hospital discharge do not necessarily lead to a higher incidence of SH, provided that perinatal home care is well organized.

Interaction of Hemolysis and Hyperbilirubinemia on Neurodevelopmental Outcomes in the Collaborative Perinatal Project

Our objective was to reanalyze data from the Collaborative Perinatal Project to investigate whether bilirubin is more neurotoxic in newborns with a positive direct antiglobulin test. The Collaborative Perinatal Project enrolled 54795 newborns at 12 centers in the United States between 1959 and 1966. We restricted our analysis to those with a birth weight of >/=2000 g and gestational age of >/=36 weeks who had follow-up at 7 to 8 years of age (n = 32808 for IQ testing; n = 33278 for neurologic examination, and n = 16354 for hearing testing). We examined the association between maximum total serum bilirubin levels and these 3 neurodevelopmental outcomes by using multiple linear and logistic regression models. We included interaction terms for the effect of bilirubin category and direct antiglobulin test result on the neurodevelopmental outcome. Overall, maximum total serum bilirubin level was not a significant predictor of IQ scores. However, there was a statistically significant interaction between a positive direct antiglobulin test and a maximum total serum bilirubin level of >/=25 mg/dL on IQ scores (eg, full-scale IQ: -6.7 points). No similar direct antiglobulin test interaction was seen for those with those with a total serum bilirubin of 20 to 24.9 mg/dL (eg, full-scale IQ: -1.7 points). We found no evidence of an interaction between a positive direct antiglobulin test and total serum bilirubin levels on the risk of an abnormal or suspicious neurologic examination or sensorineural hearing loss. In the Collaborative Perinatal Project, evidence of increased bilirubin toxicity in those with a positive direct antiglobulin test result was confined to an adverse association with IQ in those with total serum bilirubin of >/=25 mg/dL.

Short- and Long-Term Outcome of Severe Neonatal Nonhemolytic Hyperbilirubinemia

We studied the effects of hyperbilirubinemia on brainstem auditory pathways and neurodevelopmental status in 99 full-term neonates with severe nonhemolytic hyperbilirubinemia (total serum bilirubin level = 301 to 500 micromol/L) born between 1995 and 2000. These were divided into three groups: group 1, moderate hyperbilirubinemia (n = 30; mean maximum total serum bilirubin = 320.7 micromol/L or 18.9 mg%); group 2, severe hyperbilirubinemia (n = 63; mean maximum total serum bilirubin = 369.0 micromol/L or 21.7 mg%); and group 3, super hyperbilirubinemia (n = 6; mean maximum total serum bilirubin = 457.2 micromol/L or 26.9 mg%). All received phototherapy, and three neonates also had exchange transfusion. Initial brainstem auditory evoked potentials were recorded in all at the mean age of 3.1 months (range 1-9 months). At initial assessment, only nine neonates (9.1%) had abnormal brainstem auditory evoked potentials. All except two returned to normal at 2 years. These two children had a hearing threshold at 50 nHL. We then compared serial brainstem auditory evoked potentials until 2 years for these nine cases with initial abnormal brainstem auditory evoked potentials, and nine cases with initial normal brainstem auditory evoked potentials were recruited for comparison. All 99 children had regular physical, neurologic, visual, and auditory assessments every 3 to 6 months until the age of 3 years. There was no significant correlation between demographic factors (gender, gestational age, or birthweight), maximum total serum bilirubin, and total serum bilirubin at discharge with an abnormal brainstem auditory evoked potential. There was no significant difference in the rate of brainstem auditory evoked potential abnormalities between the three groups: moderate (10%), severe (7.9%), and super (16.7%). All had normal neurodevelopmental status at 3 years. Only two children had transient mild motor delay and hypotonia, and both had normal brainstem auditory evoked potentials. There was no relationship between the abnormalities of the brainstem auditory evoked potentials and neurodevelopmental status. None of the three children receiving exchange transfusion had abnormal brainstem auditory evoked potentials or neurodevelopmental outcome. With the neurophysiologic and clinical outcomes in our cohort with severe nonhemolytic hyperbilirubinemia, we propose that the toxic effect of hyperbilirubinemia on auditory brainstem pathways might be transient provided that prompt treatment is initiated.

Extreme hyperbilirubinaemia in term and near‐term infants in Denmark

To determine the incidence amongst infants born at term or near-term of extreme hyperbilirubinaemia, i.e., with a serum concentration of unconjugated bilirubin exceeding the limit above which an exchange transfusion was indicated according to the authorized guidelines. The investigation period covered 2 y, 1 January 2000 to 31 December 2001, and included all infants born alive at term or near-term in Denmark. All infants with extreme hyperbilirubinaemia admitted to paediatric departments were recorded. Thirty-two infants developed extreme hyperbilirubinaemia, i.e., an incidence of 25 per 100 000. The maximum total serum bilirubin concentration (TSB) was 492 (385-689) micromol/I (median (range)). The median value of the exchange transfusion limits was 450 micromol/l. Twelve infants had signs and symptoms of central nervous system involvement; 11 had acute bilirubin encephalopathy phase-1 symptoms; and one had phase-2 symptoms. Nineteen infants developed extreme hyperbilirubinaemia during primary admission to the maternity ward or neonatal department; the others after having been discharged. There was no difference in maximum TSB between those infants not discharged from hospital and those infants admitted to hospital from home. Maximum TSB appeared latest amongst those infants admitted from home (p < 0.01), and these more often had signs and symptoms of central nervous system involvement (p < 0.05). Ten infants were of non-Caucasian extraction. Less than half of all Danish mothers receive both verbal and written information after birth on jaundice in the infant. Twenty-five per 100 000 infants born at term or near-term developed extreme hyperbilirubinaemia, the majority of them whilst in hospital. Infants admitted from home more often had signs and symptoms of central system involvement.

Infants with bilirubin levels of 30 mg/dL or more in a large managed care organization.

To describe the incidence, etiology, treatment, and outcome of newborns with total serum bilirubin (TSB) levels >or=30 mg/dL (513 micro mol/L). Population-based case series. Eleven Northern California Kaiser Permanente Medical Care Program hospitals and 1 affiliated hospital. Eleven infants with TSB levels of >or=30 mg/dL in the first 30 days after birth, identified using computer databases from a cohort of 111,009 infants born 1995-1998. Clinical data from the birth hospitalization, rehospitalization, and outpatient visits in all infants; psychometric testing at age 5 (N = 3), neurologic examinations by child neurologists at age 5 (N = 3), or primary care providers (N = 7; mean age: 2.2 years); Parent Evaluation of Developmental Status (N = 8; mean age: 4.2 years). Maximum TSB levels of the 11 infants ranged from 30.7 to 45.5 mg/dL (525 micro mol/L to 778 micro mol/L; mean: 34.9 mg/dL [597 micro mol/L]). Four were born at 35 to 36 weeks gestation, and 7 were exclusively breastfed. Two had apparent isoimmunization; the etiology for the other 9 remained obscure, although only 4 were tested for glucose-6-phosphate dehydrogenase deficiency and 1 was bacteremic. None had acute neurologic symptoms. All received phototherapy and 5 received exchange transfusions. One infant died of sudden infant death syndrome; there was no kernicterus at autopsy. Two were lost to follow-up but were neurologically normal when last seen for checkups at 18 and 43 months. One child was receiving speech therapy at age 3. There were no significant parental concerns or abnormalities in the other children. In this setting, TSB levels >or=30 mg/dL were rare and generally unaccompanied by acute symptoms. Although we did not observe serious neurodevelopmental sequelae in this small sample, additional studies are required to quantify the known, significant risk of kernicterus in infants with very high TSB levels.

Neurodevelopmental outcome at 1 year in Zimbabwean neonates with extreme hyperbilirubinaemia.

The study concentrates on estimating the magnitude of the effect of a single risk factor, maximum total serum bilirubin (TSB) in excess of 400 micromol/l (23.4 mg/dl), on the neurodevelopmental outcome of 50, singleton, Zimbabwean neonates at 1 year of age. At 1 year corrected age the Bayley Scales of Infant Development (BSID) was administered. Two infants died and five were lost to follow up. TSB was neither associated with birth weight nor with gestational age. Of 43 infants with a TSB > 400 micromol/l (23.4 mg/dl),11(26%) scored abnormal on the BSID at 1 year of age and 5 (12%) infants developed the choreoathetoid type of cerebral palsy. Infants with bilirubin levels between 400 and 500 micromol/l (23.4 and 29.2 mg/dl) who scored abnormal or suspect on the Bayley Scales of Infant Development were preterm or had haemolytic disease. All term infants without haemolysis and with bilirubin levels between 400 and 500 micromol/l (23.4 mg/dl-29.2 mg/dl) were normal at 1 year of age.

Neurological status in severely jaundiced Zimbabwean neonates.

Neurological status was studied in 50 jaundiced infants with a total serum bilirubin of > 400 mumol/l (23.4 mg/dl). Infants were assessed in the neonatal period with the Neonatal Neurological Examination and 4 months of age with the Infant Motor Screen. Twenty-six (52 per cent) infants were premature. Analysis of variance did not show a significant difference between gestational age, birth weight, and maximum total serum bilirubin or between gestational age, birth weight, and neurological optimality score. Based on the presence of abnormal neurological syndromes the infants were classified as normal (n = 27), suspect (n = 11), or abnormal (n = 12). Serum bilirubin levels were higher (p < 0.0001) and the neonatal neurological examination scores lower (p < 0.0001) in the seven (14 per cent) infants who received an exchange transfusion. In the transfused group four out of seven infants and in the non-transfused group seven out of 43 infants were classified as abnormal (p < 0.03). The Neonatal Neurological Examination was shown to be sensitive in detecting neurodevelopmental abnormalities in the neonatal period, with a sensitivity of 83 per cent, specificity of 88 per cent, positive predictive value of 62 per cent, and negative predictive value of 96 per cent.

Extreme hyperbilirubinaemia in Zimbabwean neonates: neurodevelopmental outcome at 4 months.

As part of a prospective study of severely jaundiced Zimbabwean infants, the relationship between maximum total serum bilirubin (TSB) concentration in the neonatal period and neurodevelopmental outcome at the corrected age of 4 months was studied. Fifty infants with a TSB of > 400 micromol/l (23.4 mg/dl) were enrolled and screened with a neonatal neurological examination (NNE). The cause of jaundice was low birth weight in 22 (44%), ABO incompatability in 8 (16%), sepsis in 8 (16%) and congenital syphilis (6%) in 3 infants. In 9 infants a cause could not be determined. At 4 months, 2 infants had died and 3 were lost to follow up, leaving 45 infants for the infant motor screen (IMS) at 4 months of age. Mean TSB in the neonatal period was 485 micromol/l (28.2 mg/dl), and 7 infants received an exchange transfusion. Mean TSB of the infants with an exchange transfusion was 637 micromol/l (37.2 mg/dl) (range 429-865 micromol/l (25-50.3 mg/dl)) and of the infants without transfusion 459 micromol/l (26.8 mg/dl) (range 400 740 micromol/l (23.4-43 mg/dl)) (P < 0.0001). The TSB was not associated with birth weight, gestational age, gender or head circumference of the baby. On the IMS, 6 of 45 (13.3%) infants scored abnormal, 6 (13.3%) suspect and 33 (73%) scored normal. Three of the six (50%) remaining infants who received an exchange transfusion scored abnormal on the IMS while only 3 of the 39 (8%) infants without exchange transfusion were abnormal. More than 25% of infants with a TSB of > 400 micromol/l (23.4 mg/dl) scored abnormal or suspect at 4 months of age and half of these infants already showed irreversible neurological symptoms. All infants who scored abnormal or suspect on the IMS with bilirubin levels between 400 and 500 micromol/l (23.4 and 29.2 mg/dl) had haemolytic disease or were premature.