Biochemical characteristics of newborns with carnitine transporter defect identified by newborn screening in California.

Carnitine transporter defect (CTD; also known as systemic primary carnitine deficiency; MIM 212140) is due to mutations in the SLC22A5 gene and leads to extremely low carnitine levels in blood and tissues. Affected individuals may develop early onset cardiomyopathy, weakness, or encephalopathy, which may be serious or even fatal. The disorder can be suggested by newborn screening. However, markedly low newborn carnitine levels can also be caused by conditions unrelated to CTD, such as the low carnitine levels often associated with normal pregnancies and some metabolic disorders occurring in the mother. In order to clarify the biochemical characteristics most useful for identification of CTD in newborns, we examined California Department of Public Health newborn screening data for CTD from 2005 to 12 and performed detailed chart reviews at six metabolic centers in California. The reviews covered 14 cases of newborn CTD, 14 cases of maternal disorders (CTD, 6 cases; glutaric aciduria, type 1, 5; medium-chain acyl CoA dehydrogenase deficiency, 2; and cobalamin C deficiency, 1), and 154 false-positive cases identified by newborn screening. Our results show that newborns with CTD identified by NBS exhibit different biochemical characteristics, compared to individuals ascertained clinically. Newborns with CTD may have NBS dried blood spot free carnitine near the lower cutoff and confirmatory plasma total and free carnitine levels near the normal lower limit, particularly if obtained within two weeks after birth. These findings raise the concern that true cases of CTD may exist that could have been missed by newborn screening. CTD should be considered as a possible diagnosis in cases with suggestive clinical features, even if CTD was thought to be excluded in the newborn period. Maternal plasma total carnitine and newborn urine total carnitine values are the most important predictors of true CTD in newborns. However, biochemical testing alone does not yield a discriminant rule to distinguish true CTD from low carnitine in newborns due to other causes. Because of this biochemical variability and overlap, molecular genetic testing is imperative to confirm CTD in newborns. Additionally, functional testing of fibroblast carnitine uptake remains necessary for cases in which other confirmatory testing is inconclusive. Even with utilization of all available diagnostic testing methods, confirmation of CTD ascertained by NBS remains lengthy and challenging. Incorporation of molecular analysis as a second tier step in NBS for CTD may be beneficial and should be investigated.

Krabbe disease: clinical, biochemical and molecular information on six new patients and successful retrospective diagnosis using stored newborn screening cards.

PURPOSE: To present clinical, biochemical and molecular information on six new clinically diagnosed Krabbe disease patients and assess the sensitivity of retrospective galactocerebrosidase measurement in their newborn screening samples. METHODS: Medical records were reviewed. Galactocerebrosidase activity was measured in leukocytes and, retrospectively, in the patients' newborn screening cards (stored for 1.4 to 13.5 years). GALC gene mutation analysis was performed. RESULTS: Five patients with Krabbe disease, one of whom also had hydrocephalus, became symptomatic during infancy. A sixth patient presented with seizures and developmental regression at age two and had a protracted disease course. Galactocerebrosidase activity in leukocytes ranged from 0.00 to 0.20 nmol/h/mg protein. Low galactocerebrosidase activity (range: 3.2% to 11.1% of the daily mean), consistent with Krabbe disease, was detected in each of the newborn screening samples. GALC molecular analysis identified six previously unreported mutations and two novel sequence variants. CONCLUSION: Our cases highlight the clinical variability of Krabbe disease. Galactocerebrosidase activity in newborn dried blood spots is a highly sensitive test, even when samples have been stored for many years. The high frequency of private mutations in the GALC gene may limit the use of genetic information for making treatment decisions in the newborn period.

Extremely high phenylalanine levels in a newborn on parenteral nutrition: phenylketonuria in the neonatal intensive care unit.

A 1890-g newborn on total parenteral nutrition (TPN) had phenylalanine levels reaching 4164 µM indicating phenylketonuria (PKU). Review of 64 PKU cases from the California Newborn Screening Program disclosed another newborn diagnosed while on TPN. Phenylalanine levels rose five times faster with TPN, as estimated from rates in these infants. Thus, TPN use is associated with very high phenylalanine levels in newborns with PKU. When starting TPN soon after birth (for example, on day 1), early detection of PKU-by newborn screening 12 to 24 h after infusions are begun-should be helpful in limiting exposures to toxic levels of phenylalanine.

Maternal medium-chain acyl-CoA dehydrogenase deficiency identified by newborn screening.

Prior to the advent of expanded newborn screening, sudden and unexplained death was often the first and only symptom of medium-chain acyl-CoA dehydrogenase deficiency (MCADD). With the use of tandem mass spectrometry, infants can now be identified and treated before a life threatening metabolic decompensation occurs. Newborn screening has also been shown to detect previously undiagnosed maternal inborn errors of metabolism. We have now diagnosed two women with MCADD following the identification of low free carnitine in their newborns. While one of the women reported prior symptoms of fasting intolerance, neither had a history of metabolic decompensation or other symptoms consistent with a fatty acid oxidation disorder. These cases illustrate the importance of including urine organic acid analysis and an acylcarnitine profile as part of the confirmatory testing algorithm for mothers when low free carnitine is identified in their infants.

Maple syrup urine disease: further evidence that newborn screening may fail to identify variant forms.

Newborn screening (NBS) by tandem mass spectrometry (MS/MS) has allowed for early detection and initiation of treatment in many patients with maple syrup urine disease (MSUD) (OMIM 248600), however, a recent report suggests that variants forms may be missed. Information on these patients is limited. We present clinical, biochemical and molecular information on patients with variant forms of MSUD not detected by the California Newborn Screening Program. Between July 2005 and July 2009, 2200,000 newborns were screened in California by MS/MS. Seventeen cases of MSUD were detected and three (two siblings) were missed. Additionally, the NBS cards of two siblings with late onset MSUD, who were born pre-expanded NBS, were retrospectively analyzed. None of the five patients met criteria to be considered presumptive positive for MSUD (leucine>200micromol/L and a ratio of leucine/alanine>or=1.5). Alloisoleucine (allo-ile) was subsequently analyzed in the NBS cards of all five patients, two of whom were found to have elevated levels. The proband in each family was diagnosed following symptoms triggered by an intercurrent illness or increased protein intake. At diagnosis, leucine levels ranged between 561 and >4528micromol/L, and allo-ile ranged from 137 to 239micromol/L. Two affected siblings had normal plasma amino acids when asymptomatic; however, their biochemical profiles were diagnostic of MSUD during intercurrent illnesses. The median age at diagnosis of all patients was one year (range 0.8-6.7). Heterozygous BCKDHB (E1beta) mutations (c.832G>A/c.970C>T) were identified in one family and a homozygous DBT (E2) sequence variant (c.1430 T>G) in another. The third family had one identifiable DBT mutation (c.827T>G), however, a second mutation was not detected. This report provides further evidence that NBS by MS/MS is unable to detect all cases of MSUD. Second-tier testing with allo-ile may improve sensitivity; however, some children with variant forms will invariably be missed.

Adenovirus detection in Guthrie cards from paediatric leukaemia cases and controls.

Archived neonatal blood cards (Guthrie cards) from children who later contracted leukaemia and matched normal controls were assayed for adenovirus (AdV) C DNA content using two highly sensitive methods. In contrast to a previous report, AdV DNA was not detected at a higher frequency among neonates who later developed leukaemia, when compared with controls.

Hb H hydrops foetalis syndrome: a case report and review of literature.

Haemoglobin H (Hb H) disease is caused by deletion or inactivation of three alpha-globin genes, leaving only one intact and active alpha-globin gene. People with Hb H disease usually have moderate anaemia, but are generally thought to be asymptomatic. Some Hb H disease patients require transfusions, and there are reports of fetuses with Hb H disease who have severe anaemia in utero resulting in fatal hydrops foetalis syndrome. We now report a case of Hb H hydrops foetalis syndrome, caused by the inheritance of a hitherto novel alpha-globin gene point mutation (codon 35 TCC-->CCC or Serine-->Proline) and an alpha-thalassaemia deletion of the Filipino type removing all zeta-alpha-globin genes on the other chromosome 16. The infant was delivered prematurely because of pericardial effusion and fetal distress, and was found to have severe anaemia and congenital anomalies. A review of the relevant literature on this syndrome is presented, and serves to underscore the phenotypic variations of Hb H disease and the need for surveillance for this condition among newborns and genetic counselling in communities with a high proportion of at-risk populations.

Universal newborn screening for Hb H disease in California.

Newborn screening is an accepted public health measure to ensure that appropriate health care is provided in a timely manner to infants with hereditary/metabolic disorders. Alpha-thalassemia is a common hemoglobin (Hb) disorder, and causes Hb H (beta4) disease, and usually fatal homozygous alpha(0)-thalassemia, also known as Hb Bart's (gamma4) hydrops fetalis syndrome. In 1996, the State of California began to investigate the feasibility of universal newborn screening for Hb H disease. Initial screening was done on blood samples obtained by heel pricks from newborns, and stored as dried blood spots on filter paper. Hb Bart's levels were measured as fast-moving Hb by automated high-performance liquid chromatography (HPLC) identical to that currently used in newborn screening for sickle cell disease. Subsequent confirmation of Hb H disease was done by DNA-based diagnostics for alpha-globin genotyping. A criterion of 25% or more Hb Bart's as determined by HPLC detects most, if not all cases of Hb H disease, and few cases of alpha-thalassemia trait. From January, 1998, through June, 2000, 89 newborns were found to have Hb H disease. The overall prevalence for Hb H disease among all newborns in California is approximately 1 per 15,000. Implementation of this program to existing newborn hemoglobinopathy screening in populations with significant proportions of southeast Asians is recommended. The correct diagnosis would allow affected infants to be properly cared for, and would also raise awareness for the prevention of homozygous alpha(0)-thalassemia or Hb Bart's hydrops fetalis syndrome.

Use of the phenylalanine:tyrosine ratio to test newborns for phenylketonuria in a large public health screening programme.

OBJECTIVE: To assess the benefits of using the phenylalanine:tyrosine ratio to screen newborns for phenylketonuria (PKU). SETTING: Data were collected from all newborns in California during a ten month period (n = 404,381). METHODS: Dried blood spot specimens were analysed at nine laboratories. To assure that the results reported from multiple sites were matched accurately, an automated methodology was chosen that included sample processing, analysis, telecommunications, reporting, and information technology. Phenylalanine and tyrosine concentrations were measured independently by continuous flow fluorometry, for which precision, recovery, detection limits, carryover, chemical specificity, reportable range, and number of repeats are reported. RESULTS: In this study, 37% of the newborns were tested at less than 24 hours of age. For this population, using a phenylalanine only cut off of 200 mumol/l, there were 48 recalled infants per case of classic PKU. Using the phenylalanine:tyrosine ratio with a cut off of 1.50, screen positives could be reported with phenylalanine as low as 150 mumol/l and with only 12 recalls per case. CONCLUSIONS: The phenylalanine:tyrosine ratio can be measured accurately at multiple laboratories using two channel chemical analyses. Having applied the methods to the routine clinical screening of a large population, it was confirmed that the clinical sensitivity and specificity of the PKU screening test are higher when the phenylalanine:tyrosine ratio is incorporated into the cut off than when the cut off is based on the phenylalanine concentration alone.

Asian immigration and public health in California: thalassemia in newborns in California.

PURPOSE: This study reviews Asian immigration in California and the effect it has had on public health in the state in terms of genetic disease detection. This is documented in terms of the numbers of cases of thalassemia detected, including Hemoglobin (Hb) E/beta-thalassemia, beta-thalassemia major, and Hb H disease. PATIENTS AND METHODS: California has been screening all newborns for hemoglobinopathies since 1990 and tests approximately 530,000 newborns per year. Samples are collected on filter paper during the first I to 2 days of life and sent to one of eight contract laboratories. The screening methodology is cation exchange high-performance liquid chromatography. Confirmatory testing is performed at Children's Hospital Oakland hemoglobin laboratory using a variety of methods. RESULTS: Approximately five to seven cases each of Hb E/beta-thalassemia and beta-thalassemia major are detected annually. Most cases are of Southeast Asian origin. Prevalence rate of Hb E/beta-thalassemia among Southeast Asians is approximately 1 in 2,200 births. A pilot program for Hb H disease screening was successful and this disorder has now been incorporated in newborn screening, detecting approximately 40 cases per year. CONCLUSIONS: Increases in Asian immigration and births in the U.S., particularly California, have been dramatic during the past 10 years and have led to detection of previously rare diseases like Hb E/beta-thalassemia. It has also changed the way other thalassemic disorders are viewed, such as Cooley anemia, which previously affected mainly individuals of Mediterranean origin. Now, most affected patients are of Asian origin.

Risk factors for congenital hypothyroidism: an investigation of infant's birth weight, ethnicity, and gender in California, 1990-1998.

BACKGROUND: Approximately 85% of primary congenital hypothyroidism (CH) is sporadic and due to malformations of the thyroid gland. Past studies have reported an increased birth weight among infants with CH. We have attempted to replicate and expand these observations, examining the association between different birth weight categories and CH stratified by infant's sex. We have also examined the prevalence of CH by mother's age and infant's ethnicity, gender, and year of birth. METHODS: A cross-sectional study was conducted on 5, 049,185 infants screened by the statewide California Newborn Screening Program between 1990 and 1998, an estimated 98.6% of all newborns in the state. Dried blood spots from a heel stick were assayed for thyroxine (T4), and presumptive positives had follow-up assays of thyroid-stimulating hormone (TSH) to determine definite positives. RESULTS: A total of 1,806 cases of CH were identified. The following findings are unlikely to be due to chance. Compared with infants with birth weights of 3,000-3,499 g, infants weighing <2,000 g and those weighing >/=4,500 g had a twofold or greater increase in the prevalence of CH. This was not explained as a result of confounding by the infant's ethnicity or gender. Compared with whites, elevated prevalence rates were found in most ethnic groups, which include the following: Hispanics, Chinese, Vietnamese, Asian Indians, Filipinos, Middle Easterners, and Hawaiians. As reported previously, black infants had about one-third the prevalence rate of whites. We also observed the frequently described female preponderance of CH. The female excess was maintained at all birth weights, however it varied by infant's ethnicity. Trends in the prevalence of CH were not associated with mother's age or with the time interval between 1990 and 1998. CONCLUSIONS: We observed an increased risk of CH in both low-birth-weight (<2,000-g) and macrosomic (>/=4,500-g) infants. This U-shaped association has not been described in past studies. We have also expanded the previously described ethnic differences in CH risk to include ethnic groups not previously studied. The unique pattern of CH occurrence suggests that further studies to define modifiable risk factors may be useful.

Prenatal ultrasound findings in affected and unaffected pregnancies that are screen-positive for trisomy 18: the California experience.

This study investigated whether significant differences in ultrasound findings exist between trisomy 18 affected and unaffected pregnancies positive by serum screening. Ultrasound reports were reviewed for 335 screen-positive women. This represented 65% of all trisomy 18 screen-positive patients who had follow-up services at any of 117 Californian state-approved Prenatal Diagnosis Centers during a six-month period from November 1, 1995 to April 30, 1996. Ultrasound reports were available for 100% of trisomy 18 fetuses diagnosed during the six month period (n=23). Ultrasound findings were reported as normal in 35% of the fetuses affected with trisomy 18. The number and type of abnormalities observed in the affected and unaffected groups are described. When compared to unaffected cases, the trisomy 18 affected fetuses had a greater re-dating discrepancy on follow-up ultrasound evaluation and significantly lower femur length to biparietal diameter (FL/BPD) ratio measurements. We recommend that all women who are screen positive for trisomy 18 be encouraged to have amniocentesis, regardless of ultrasound findings, since affected fetuses may not be detected otherwise.

Sickle-cell disease not identified by newborn screening because of prior transfusion.

Erythrocyte transfusion can impair detection of sickle-cell disease, galactosemia, or biotinidase deficiency with newborn screening. We report on 4 infants with SCD in whom delayed diagnosis was associated with neonatal transfusion. In 2 cases, the initial newborn screening showed no hemoglobin S. In no case was the recommended screening >/=120 days from the last transfusion obtained. Two children had significant SCD-related morbidity before diagnosis.

Neural tube defect prevalence in California (1990-1994): eliciting patterns by type of defect and maternal race/ethnicity.

This study presents race/ethnicity-specific prevalence estimates of neural tube defects (NTDs) in California using 5 years of population-based data. NTD prevalence estimates include prenatally diagnosed cases, as well as cases diagnosed at birth. The California NTD Registry contains NTD case reports identified through the California Maternal Serum Alpha-Feto Protein (AFP) Screening Program, the California Birth Defects Monitoring Program, and additional reports from clinicians and clinics throughout the state. These data were used to estimate NTD prevalence in a large population-based study (n = 1,618,279). The overall NTD prevalence among White, Black, Hispanic, and Asian women are reported, as well as race/ethnic prevalence, for anencephaly, spina bifida, and encephalocele. Rates are expressed as the number of cases per 1,000 women screened between 1990 and 1994. Among 1,457 women with an NTD-affected pregnancy, the overall rate for anencephaly, spina bifida, and encephalocele was 0.49 (95% CI 0.46-0.53), 0.42 (95% CI 0.38-0.45), and 0.08 (95% CI 0.07-0.09), respectively. When these types of NTDs are combined, Hispanic women had the highest overall rate (1.12, 95% CI 1.04-1.21), followed by Whites (0.96, 95% CI 0.89-1.04), Blacks (0.75, 95% CI 0.59-0.91), and Asians (0.75, 95% CI 0.60-0.90). Hispanic women were 45% more likely than White women to have a pregnancy affected with anencephaly (odds ratio = 1.45, 95% CI 1.24-1.70), while Asian women were over two times less likely to have a pregnancy affected with spina bifida (odds ratio = 0.44, 95% CI 0.29-0.65). Considerable variation exists in the prevalence of NTDs by race/ethnicity and by type of NTD, with Hispanic women exhibiting the highest overall NTD rate.

Use of phenylalanine-to-tyrosine ratio determined by tandem mass spectrometry to improve newborn screening for phenylketonuria of early discharge specimens collected in the first 24 hours.

We compared the screening interpretation of fluorometric analytical results for phenylketonuria (PKU) with tandem mass spectrometry (MS/MS) in filter paper blood spots collected from newborns <24 h of age. In MS/MS, both Phe and Tyr are quantified. Two hundred and eight blood spots collected from infants <24 h of age were retrieved from storage from the California newborn screening program. These samples had been categorized on the basis of fluorometric analysis as initial negative, initial positive for hyperphenylalaninemia with negative determination on recall, or initial positive for hyperphenylalaninemia and confirmed on follow up as PKU or variant hyperphenylalaninemia. The retrieved samples were analyzed in a blinded fashion using MS/MS. Correlation analysis of fluorometry vs MS/MS for Phe concentration was high, with a Pearson correlation coefficient of 0.817. When 180 micromol/L was used as the cutoff Phe concentration for MS/MS and 258 micromol/L was used as the cutoff for fluorometry, all infants with confirmed classical PKU and variant hyperphenylalaninemia were detected. MS/MS analysis reduced the number of false-positive results from 91 to 3. Simultaneous quantification of Phe and Tyr by MS/MS with the use of a cutoff Phe/Tyr molar ratio of 2.5 further reduced the number of false positives to 1. Samples from affected infants showed a discernible trend of increasing Phe concentration and Phe/Tyr molar ratio with age of collection. These results demonstrate the utility of MS/MS in the routine PKU screening of early-discharge newborns. MS/MS reduces the false-positive rate of fluorometric screening almost 100-fold because of the improved accuracy and precision of Phe measurement and simultaneous confirmation with the Phe/Tyr molar ratio. In addition to the detection of PKU, MS/MS can also detect other aminoacidopathies and disorders of fatty acid and organic acid metabolism with lower false-positive rates than other methods currently used in newborn screening programs.

Epidemiologic study of Down syndrome in a racially diverse California population, 1989-1991.

The prevalence of Down syndrome was studied among all live births occurring between 1989 and 1991 in the California counties monitored by the California Birth Defects Monitoring Program. Objectives of this study were: 1) to calculate adjusted prevalence rates and quinquennial maternal age-specific risk rates of Down syndrome after adjusting for elective abortion of prenatally diagnosed fetuses; 2) to estimate the impact of prenatal diagnosis and subsequent elective abortion of affected fetuses on the observed prevalence of Down syndrome; and 3) to examine sex ratios among liveborn infants and fetuses with Down syndrome. The racial/ethnic diversity and large size of the population allowed the data to be stratified into five racial categories-Hispanics, whites, Asians, blacks, and others. For the period 1989-1991, the observed prevalence of Down syndrome was 1.13 per 1,000 live births, and the adjusted total prevalence, which took into account the termination of affected pregnancies following prenatal diagnosis, was 1.53 per 1,000 live births. In a comparison of quinquennial maternal age-specific risk rates of Down syndrome by race, Hispanics and whites were the only groups with rates that differed significantly from each other, with Hispanics exhibiting higher rates at maternal ages under 40 years. The overall reduction in live births with Down syndrome in 1989-1991 that could be attributed to prenatal diagnosis and elective abortion of affected fetuses was 25.8%, with a 49.1% reduction being observed at maternal ages > or = 35 years. In 1990-1991, Hispanics had the lowest overall reduction (10.0%), while whites had the highest reduction (46.3%). The male: female ratios among liveborns with Down syndrome were significantly higher than those among all live births, and race had a significant association with sex ratios in both cases and controls. These findings indicate that prenatal diagnosis and elective termination of affected pregnancies has had a substantial impact in reducing the number of liveborns with Down syndrome in the monitored California counties. The effect was greatest for whites and least for Hispanics, with results indicating considerable variation in the use of prenatal diagnostic services among racial/ethnic groups. Estimates of adjusted total prevalence and reduction in live births with Down syndrome in this study should be considered minimal because of some underascertainment of prenatally diagnosed cases.

Beta-globin haplotypes from blood spots for follow-up of newborn hemoglobinopathy screening.

The inheritance of sickle-cell anemia upon the background of the major beta-globin gene cluster haplotypes has been associated with differing risks for major organ failure, and more recently with response to hydroxyurea treatment. Early identification of beta-globin haplotypes in individuals with sickle-cell anemia may be a clinically useful prognostic factor for severity of disease expression. This report describes the use of whole-blood spots on filter papers from newborn hemoglobinopathy screening for beta-globin gene cluster haplotyping by the polymerase chain reaction.

Sex ratios in fetuses and liveborn infants with autosomal aneuploidy.

Ten data sources were used substantially to increase the available data for estimating fetal and livebirth sex ratios for Patau (trisomy 13), Edwards (trisomy 18), and Down (trisomy 21) syndromes and controls. The fetal sex ratio estimate was 0.88 (N = 584) for trisomy 13, 0.90 (N = 1702) for trisomy 18, and 1.16 (N = 3154) for trisomy 21. All were significantly different from prenatal controls (1.07). The estimated ratios in prenatal controls were 1.28 (N = 1409) for CVSs and 1.06 (N = 49427) for amniocenteses, indicating a clear differential selection against males, mostly during the first half of fetal development. By contrast, there were no sex ratio differences for any of the trisomies when comparing gestational ages < 16 and > 16 weeks. The livebirth sex ratio estimate was 0.90 (N = 293) for trisomy 13, 0.63 (N = 497) for trisomy 18, and 1.15 (N = 6424) for trisomy 21, the latter two being statistically different than controls (1.05) (N = 3660707). These ratios for trisomies 13 and 18 were also statistically different than the ratio for trisomy 21. Only in trisomy 18 did the sex ratios in fetuses and livebirths differ, indicating a prenatal selection against males > 16 weeks. No effects of maternal age or race were found on these estimates for any of the fetal or livebirth trisomies. Sex ratios for translocations and mosaics were also estimated for these aneuploids. Compared to previous estimates, these results are less extreme, most likely because of larger sample sizes and less sample bias. They support the hypothesis that these trisomy sex ratios are skewed at conception, or become so during embryonic development through differential intrauterine selection. The estimate for Down syndrome livebirths is also consistent with the hypothesis that its higher sex ratio is associated with paternal nondisjunction.