Polymorphic variants of genes related to arginine metabolism and the risk of orofacial clefts

OBJECTIVE

Maternal mid-pregnancy low levels of symmetric dimethylarginine and newborn low levels of citrulline are suspected to be risk factors for orofacial clefts. This study was undertaken to investigate the involvement of polymorphic variants of genes related to arginine metabolism in the susceptibility of clefting.

DESIGN

PCR-RFLP and HRM analyses were used to analyze single nucleotide polymorphisms (SNPs) of ASS1, ASL, and SLC25A13 in 172 children with non-syndromic cleft lip with or without cleft palate (CL/P) and 188 controls without congenital anomalies. The differences in allele and genotype frequencies between cases and controls were determined using standard Chi-square and Fisher exact tests. The odds ratio (OR) and associated 95% confidence intervals (95% CI) for individuals with CL/P versus controls were also calculated. Associations between the investigated polymorphisms and the risk of being born with an orofacial cleft were tested using the nonparametric and genetic model-free Multifactor Dimensionality Reduction (MDR) approach.

RESULTS

Analysis of five SNPs of the ASS1 gene revealed that the G allele of rs7860909 is associated with increased CL/P risk. Compared to individuals with the AA genotype, the G allele carriers had an OR of 1.768 (95% CI: 1.133-2.759; p=0.012). For the remaining SNPs of all analysed genes, there was no overall evidence for cleft association considering the allele and genotype distribution. However, gene-by-gene interaction analysis conducted using the MDR approach revealed a significant interactive genetic effect of ASS1 (rs666174) and SLC25A13 (rs10252573) on the occurrence of clefting (p=0.002).

CONCLUSION

Our results demonstrate moderate evidence for the association of polymorphic variants of genes related to arginine metabolism with abnormal palatogenesis.

Newborn Screening of Lysosomal Storage Disorders

Background: Newborn screening is a state-based public health program established as a means for the early detection and treatment of certain medical conditions to minimize developmental disability and mortality. The program was initiated more than 40 years ago to detect and prevent phenylketonuria. Recent technological advances have expanded the scope of newborn screening to include more than 30 inborn errors of metabolism. Consideration is now being given to inclusion of screening for lysosomal storage disorders (LSDs).

Content: Some lysosomal storage disorders (LSDs) express early in infancy or childhood and are treatable. Initiation of treatment in presymptomatic patients or in syptomatic patients before important symptoms are present may improve the long-term outcome. Therefore, early diagnosis is critical. Based on the availability of therapy and development of a screening method, 6 of the more than 40 known LSDs are candidates for newborn screening in the US: Gaucher disease, Pompe disease, Fabry disease, Niemann-Pick disease, mucopolysaccharidosis I, and Krabbe disease. This report reviews the history of newborn screening, the technology that has allowed for expanded screening during the last decade, LSDs and their treatment, and the evolving methods that might allow additional expansion of newborn screening to include certain LSDs.

Summary: Recent and evolving technological advances may be implemented for newborn screening for LSDs. This screening will identify presymptomatic newborns, allowing for early treatment and prevention or limitation of morbidity otherwise associated with these inherited rare diseases.

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.

Fatty acid oxidation disorders: maternal health and neonatal outcomes

Mitochondrial fatty acid beta-oxidation (FAO) disorders have become an important group of inherited metabolic disorders causing serious pediatric and maternal morbidity and mortality. More than 20 defects affecting beta-oxidation have been discovered, characterized by distinct enzyme or transporter deficiencies. This growing number of FAO disorders covers a wide spectrum of phenotypes and are characterized by a wide array of clinical presentations. We discuss the major mitochondrial FAO disorders and the impact they have on maternal health and neonatal outcomes; diagnostic tools and the value of genetic screening are reviewed; and current therapeutic approaches and management strategies are discussed.

Silent increase of urinary ethylmalonic acid is an indicator of nonspecific brain dysfunction

Our aim was to compare urinary ethylmalonic acid (EMA) levels in subjects who had no apparent clinical reason to have increased levels of this substance but were suffering from non-specific CNS impairment, and healthy controls. Urinary EMA concentrations detected by (1)H-NMR spectroscopy were studied in 130 subjects with CNS impairment of unknown origin (with no definite diagnosis, no specific symptoms or signs, and normal common biochemical and metabolic screening results) and 130 age- and sex-matched healthy subjects. EMA levels exceeding two standard deviations (SD) above normal (i.e. 8.1 mmol/molCn) were found in a subgroup of CNS-impaired patients and healthy controls. EMA levels exceeding 2 SD above normal were fourfold prevalent in the urine of patients with non-specific CNS impairment compared to from the EMA levels in healthy controls. Moreover, we found that the level exceeding > 8.1 mmol/molCn (i.e. > + 2 SD) had sufficient discrimination accuracy in identifying subjects with non-specific CNS impairment; the level exceeding 12 mmol/molCn (i.e. > + 6 SD) reaches suitable accuracy (i.e. 100% specificity and 78.6% sensitivity). These observations are of importance, as we found that subtle increases in urinary EMA levels are frequent in patients with non-specific CNS impairment. The reasons for this association remain unknown.

Measurement of plasma/serum acylcarnitines using tandem mass spectrometry

Acylcarnitine analysis using tandem mass spectrometry has become a powerful tool in the investigation of pediatric patients presenting with clinical signs and symptoms suggestive of fatty acid oxidation defects. These signs are diverse and include failure to thrive, feeding difficulties, and cardiomyopathy. Because the signs and symptoms are nonspecific, the identification of acylcarnitines characteristic of these inherited diseases is necessary for diagnosis. We describe a method for the analysis of acylcarnitines in plasma or serum samples using electrospray ionization tandem mass spectrometry.

Lack of genotype-phenotype correlations and outcome in MCAD deficiency diagnosed by newborn screening in New York State

INTRODUCTION

Medium chain acyl-CoA dehydrogenase (MCAD) deficiency is one of the most common inborn errors of metabolism. Affected patients have impaired ability to break down medium chain fatty acids during fasting, and typically present in the early years of life with hypoketotic hypoglycemia, Reye syndrome-like symptoms, brain damage or death. The development of newborn screening (NBS) for MCAD deficiency has greatly improved outcome, but some patients still appear at risk for severe complications. We reviewed the outcome of patients identified with MCAD deficiency by the New York State NBS process to identify biochemical or genotypic markers which might predict outcome.

METHOD

All eight NBS follow-up centers in New York State contributed the cases of MCAD deficiency diagnosed by newborn screen, who received diagnostic and follow-up care in their clinic. Data reviewed included gender, age, birthweight, initial NBS octanoylcarnitine level (C8) and C8/C2 ratio, follow-up C8 and hexanoylglycine, race/ethnicity, and presence of neonatal or later symptoms.

RESULTS

We identified 53 cases of MCAD deficiency. More than one quarter of patients had a post-neonatal symptomatic admission (predominantly lethargy associated with an intercurrent illness). No genotype or C8 level was protective for neonatal or later symptoms. There was a relationship between initial C8 level or C8/C2 ratio and occurrence of later symptoms (7.3 micromol/L in the asymptomatic vs. 19.1 micromol/L in the symptomatic, p<0.0002 for C8, and 0.26 vs. 0.6, respectively, for C8/C2 ratio, p<0.012). Four infants had initial C8 level >30 micromol/L; these infants had a high rate of symptomatic or multiple symptomatic episodes or a history of sibling death from "SIDS", and typically had deletion, nonsense or splice sites mutations. Infants having a history of a symptomatic episode were more likely to have higher initial C8 on NBS and a genotype predicted to strongly affect protein function. In our ethnically diverse group of patients, the c.985A>G mutation was rarely found in non-Caucasians.

DISCUSSION

No genotype or metabolite profile is protective from symptoms. The strong relationship between initial C8 level and outcome suggests that in at least some cases neonates having high initial C8 levels may be demonstrating an increased susceptibility to catabolic stress, and may merit additional precautions. Our data also suggest that these infants are more likely to carry severe mutations including homozygosity for the common mutation, deletions, nonsense or splice site mutations. The reports of significant lethargy or hypoglycemia during intercurrent illness in over one quarter of cases even when early medical intervention is recommended (and even when initial C8 is not profoundly elevated) underscores the importance of continued vigilance to prevent stressful fasting in this disorder.

Very long-chain acyl-CoA dehydrogenase deficiency in a patient with normal newborn screening by tandem mass spectrometry

Very long-chain acyl-CoA dehydrogenase deficiency (VLCADD) can be detected through newborn screening with tandem mass spectrometry. We report a patient who died as a result of severe brain injury due to hypoglycemia. Newborn screening was normal. Postmortem enzyme analysis and molecular testing confirmed the diagnosis of VLCADD.

Reduced levels of hydroxylated, polyunsaturated ultra long-chain fatty acids in the serum of colorectal cancer patients: implications for early screening and detection

BACKGROUND

There are currently no accurate serum markers for detecting early risk of colorectal cancer (CRC). We therefore developed a non-targeted metabolomics technology to analyse the serum of pre-treatment CRC patients in order to discover putative metabolic markers associated with CRC. Using tandem-mass spectrometry (MS/MS) high throughput MS technology we evaluated the utility of selected markers and this technology for discriminating between CRC and healthy subjects.

METHODS

Biomarker discovery was performed using Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). Comprehensive metabolic profiles of CRC patients and controls from three independent populations from different continents (USA and Japan; total n = 222) were obtained and the best inter-study biomarkers determined. The structural characterization of these and related markers was performed using liquid chromatography (LC) MS/MS and nuclear magnetic resonance technologies. Clinical utility evaluations were performed using a targeted high-throughput triple-quadrupole multiple reaction monitoring (TQ-MRM) method for three biomarkers in two further independent populations from the USA and Japan (total n = 220).

RESULTS

Comprehensive metabolomic analyses revealed significantly reduced levels of 28-36 carbon-containing hydroxylated polyunsaturated ultra long-chain fatty-acids in all three independent cohorts of CRC patient samples relative to controls. Structure elucidation studies on the C28 molecules revealed two families harbouring specifically two or three hydroxyl substitutions and varying degrees of unsaturation. The TQ-MRM method successfully validated the FTICR-MS results in two further independent studies. In total, biomarkers in five independent populations across two continental regions were evaluated (three populations by FTICR-MS and two by TQ-MRM). The resultant receiver-operator characteristic curve AUCs ranged from 0.85 to 0.98 (average = 0.91 +/- 0.04).

CONCLUSIONS

A novel comprehensive metabolomics technology was used to identify a systemic metabolic dysregulation comprising previously unknown hydroxylated polyunsaturated ultra-long chain fatty acid metabolites in CRC patients. These metabolites are easily measurable in serum and a decrease in their concentration appears to be highly sensitive and specific for the presence of CRC, regardless of ethnic or geographic background. The measurement of these metabolites may represent an additional tool for the early detection and screening of CRC.

Newborn screening and early biochemical follow-up in combined methylmalonic aciduria and homocystinuria, cblC type, and utility of methionine as a secondary screening analyte

INTRODUCTION

Combined methylmalonic aciduria and homocystinuria, cobalamin C (cblC) type, is an inherited disorder of vitamin B(12) metabolism caused by mutations in MMACHC. CblC typically presents in the neonatal period with neurological deterioration, failure to thrive, cytopenias, and multisystem pathology including renal and hepatic dysfunction. Rarely, affected individuals present in adulthood with gait ataxia and cognitive decline. Treatment with hydroxocobalamin may ameliorate the clinical features of early-onset disease and prevent clinical late-onset disease. Propionic acidemia (PA), methylmalonic acidemia (MMA), and various disorders of cobalamin metabolism are characterized by elevated propionylcarnitine (C3) on newborn screening (NBS). Distinctions can be made between these disorders with secondary analyte testing. Elevated methionine is already routinely used as a NBS marker for cystathionine beta-synthase deficiency. We propose that low methionine may be useful as a secondary analyte for specific detection of cbl disorders among a larger pool of infants with elevated C3 on NBS.

METHODS

Retrospective analysis of dried blood spot (DBS) data in patients with molecularly confirmed cblC disease.

RESULTS

Nine out of ten patients with confirmed cblC born in New York between 2005 and 2008 had methionine below 13.4mumol/L on NBS. Elevated C3, elevated C3:C2 ratio, and low methionine were incorporated into a simple screening algorithm that can be used to improve the specificity of newborn screening programs and provide a specific and novel method of distinguishing cblC from other disorders of propionate metabolism prior to recall for confirmatory testing.

CONCLUSIONS

It is anticipated that this algorithm will aid in early and specific detection of cobalamin C, D, and F diseases, with no additional expense to NBS laboratories screening for organic acidemias and classical homocystinuria.

Projected costs, risks, and benefits of expanded newborn screening for MCADD

OBJECTIVE

To evaluate the cost-effectiveness of newborn screening for medium-chain acyl-coenzyme A dehydrogenase deficiency (MCADD) incorporating quality-of-life effects for false-positive newborn screens and recommended dietary treatment.

METHODS

A computer simulation model was developed to predict costs and health outcomes for expanded newborn screening for MCADD compared with clinical identification. The modeled target population was a hypothetical cohort of 100 000 newborns in the United States. Probabilities, costs, and quality-of-life weights were derived from a long-term follow-up study of newborn screening compared with clinical identification, primary data collection, published data, and expert opinion. We used a lifetime time horizon and the societal perspective. The main outcome measure was the incremental cost-effectiveness ratio in dollars per quality-adjusted life-year (QALY) gained. Secondary outcomes included averted deaths and hospitalizations.

RESULTS

Using base-case assumptions, the cost-effectiveness of newborn screening for MCADD was $21 273 per QALY gained. The cost-effectiveness ratio increased to $21 278/QALY when the loss in quality of life associated with false-positive test results was incorporated and to $27 423/QALY when the quality of life associated with lifelong dietary recommendations for treating MCADD was incorporated. Results were sensitive to the false-positive rate for the newborn screening test and the cost of the initial screen.

CONCLUSIONS

Expanded newborn screening for MCADD is cost-effective compared with well-accepted pediatric health interventions. Losses in quality of life associated with dietary treatment for MCADD, however, may offset some of the gains in QALYs from newborn screening. Consideration of new disorders for expanded newborn screening panels should include the potential reduction in quality of life associated with treatments.

The potential of mass spectrometry for the global profiling of parasite metabolomes

The strengths and limitations of existing mass spectrometry methods for metabolite detection and identification are discussed. A brief review is made of the methods available for quenching and extraction of cells or organisms prior to instrumental analysis. The techniques available for carrying out mass spectrometry-based profiling of metabolomes are discussed using the analysis of extracts from trypanosomes to illustrate various points regarding methods of separation and mass spectrometric analysis. The advantages of hydrophilic interaction chromatography (HILIC) for the analysis of polar metabolites are discussed. The challenges of data processing are outlined and illustrated using the example of ThermoFisher's Sieve software. The existing literature on applications of mass spectrometry to the profiling of parasite metabolomes is reviewed.

Dissection of biochemical borderline phenotypes in carriers and genetic variants of medium-chain acyl-CoA dehyrogenase deficiency: implications for newborn screening [corrected]

Medium-chain acyl-CoA dehydrogenase deficiency (MCADD) represents a potentially fatal fatty acid beta-oxidation disorder. Newborn screening (NBS) by tandem mass spectrometry (MS/MS) has been implemented worldwide, but is associated with unresolved questions regarding population heterogeneity, burden on healthy carriers, cut-off policies, false-positive and negative rates. In a retrospective case-control study, 333 NBS samples showing borderline acylcarnitine patterns but not reaching recall criteria were genotyped for the two most common mutations (c.985A>G/c.199C>T) and compared with genotypes and acylcarnitines of 333 controls, 68 false-positives, and 34 patients. c.985A>G was more frequently identified in the study group and false-positives compared to controls (1:4.3/1:2.3 vs. 1:42), whereas c.199C>T was found more frequently only within the false-positives (1:23). Biochemical criteria were devised to differentiate homozygous (c.985A>G), compound heterozygous (c.985A>G/c.199C>T), and heterozygous individuals. Four false-negatives were identified because our initial algorithm required an elevation of octanoylcarnitine (C(8)) and three secondary markers in the initial and follow-up sample. The new approach allowed a reduction of false-positives (by defining high cut-offs: 1.4 micromol/l for C(8); 7 for C(8)/C(12)) and false-negatives (by sequencing the ACADM gene of few suspicious samples). Our validation strategy is able to differentiate healthy carriers from patients doubling the positive predictive value (42-->88%) and to target NBS to MCADD-subsets with potentially higher risk of adverse outcome. It remains controversial, if NBS programs should aim at identifying all subsets of all diseases included. Because the natural course of milder variants cannot be assessed by observational studies, our strategy could serve as a general model for evaluation of MS/MS-based NBS.

The profile of newborn screening coverage in China

Objective

To estimate provincial, regional and national newborn screening coverage throughout China.

Method

Information about newborn screening was collected using a survey questionnaire from neonatal screening laboratories in China in 2006–2007. The total number of live births at the provincial and national levels was obtained from the Maternal and Child Health Information System (MCHIS) and the State Statistics Bureau (SSB), respectively, and was used to calculate the neonatal screening coverage at the provincial, regional and national levels.

Results

There were 185 laboratories providing neonatal screening services in China in 2007. The rates of national screening coverage in 2006 and 2007 were 31.27% and 39.96%, respectively, based on live birth numbers reported by the SSB. Both of these estimates are lower than those calculated from live birth numbers reported by the MCHIS. The rates of coverage in the Eastern, Middle and Western regions were about 84.90%, 30.41% and 19.82%, respectively, based on the live birth numbers reported by the MCHIS.

Conclusion

There are disparities in screening coverage between regions and between provinces throughout China, but the extent of this is difficult to ascertain because of the different systems of reporting live births. To calculate nationwide screening coverage it is probably appropriate to use the SSB data on live births. However, for provincial screening coverage the calculation is probably best based on the number of live births reported by the MCHIS once the validity of the MCHIS data is verified.

False-positive newborn screening mimicking glutaric aciduria type I in infants with renal insufficiency

Glutaric aciduria type I (GA I), an autosomal-recessive deficiency of glutaryl-CoA-dehydrogenase, leads to encephalopathic crises resulting in irreversible neurological damage. As early diagnosis and implementation of appropriate treatment has significant benefit for these patients, GA I has been implemented in the extended newborn screening program in several countries. Screening parameter is glutarylcarnitine (C5DC) with its ratios. From 1 January 2005 until 31 December 2008, 173,846 newborns were examined by neonatal screening in our screening center. C5DC and/or at least three C5DC/acylcarnitine ratios were increased in 53 newborns (0.03%) and persisted in 11 infants after recall. GA I was not confirmed in any of these infants, but all 11 infants were suffering from renal insufficiency due to congenital (5/11) or acquired (6/11) renal disease. C5DC was shown to be significantly associated with renal affection and was significantly higher in infants with congenital renal insufficiency than in those with acquired renal insufficiency (p = 0.011). Creatinine correlated significantly with C5DC (p = 0.001) and all C5DC/acylcarnitine ratios, mainly with C5DC/(C8 + C10), C5DC/C0, C5DC/C2, C5DC/C4, and C5DC/C8 (for all: p = 0.001). Glutarylcarnitinemia associated with renal insufficiency has not yet been studied systematically. Renal damage in neonates might lead to disturbances in renal transporter systems of glutaric acid and its metabolites and a decreased excretion of C5DC, thus resulting in an increase of plasma C5DC. Therefore, newborns presenting with a positive screening indicating GA I may be considered not only to suffer from GA I but from renal insufficiency as well.

Enzymatic evaluation of glutaric acidemia type 1 by an in vitro probe assay of acylcarnitine profiling using fibroblasts and electrospray ionization/tandem mass spectrometry (MS/MS)

Glutaric acidemia type 1 (GA1) is usually diagnosed with an accumulation of glutaric acid (GA) or 3-hydroxyglutaric acid by GC/MS. In some cases, however, excretion of GA is low. We investigated enzymatic evaluation of GA1 using fibroblasts and MS/MS. After loading substrates, lysine, 2-aminoadipate (2AA), or GA, in fibroblasts, and incubating for 96 h, glutarylcarnitine (C5DC) levels in the media were measured. A significant increase of C5DC was observed in GA1 patients, irrespective of substrates added. 2AA showed the largest difference between patients and controls (p = 0.0004). Results suggested enzymatic evaluation of GA1 is useful under appropriate culture conditions.

A Delphi clinical practice protocol for the management of very long chain acyl-CoA dehydrogenase deficiency

INTRODUCTION

Very long chain acyl-CoA dehydrogenase (VLCAD) deficiency is a disorder of oxidation of long chain fat, and can present as cardiomyopathy or fasting intolerance in the first months to years of life, or as myopathy in later childhood to adulthood. Expanded newborn screening has identified a relatively high incidence of this disorder (1:31,500), but there is a dearth of evidence-based outcomes data to guide the development of clinical practice protocols. This consensus protocol is intended to assist clinicians in the diagnosis and management of screen-positive newborns for VLCAD deficiency until evidence-based guidelines are available.

METHOD

The Oxford Centre for Evidence-based Medicine system was used to grade the literature review and create recommendations graded from A (evidence level of randomized clinical trials) to D (expert opinion). Delphi was used as the consensus tool. A panel of 14 experts (including clinicians, diagnostic laboratory directors and researchers) completed three rounds of survey questions and had a face-to-face meeting.

RESULT

Panelists reviewed the initial evaluation of the screen-positive infant, diagnostic testing and management of diagnosed patients. Grade C and D consensus recommendations were made in each of these three areas. The panel did not reach consensus on all issues, particularly in the dietary management of asymptomatic infants diagnosed by newborn screening.

Economic evaluation of tandem mass spectrometry newborn screening in Australia

OBJECTIVE

The goal was to investigate the cost-effectiveness of tandem mass spectrometry screening for the detection of inborn metabolic errors in an Australian setting.

METHODS

Cost-effectiveness analysis from the health service perspective was undertaken on the basis of registry data for affected individuals. The intervention group was contrasted with both a contemporaneous group in nonscreening states and a historical cohort. The registry covers all individuals identified in Australia between 1994 and 2002. Main outcome measures were the total net cost of screening, the cost of treatment, life-years saved, and deaths averted.

RESULTS

The total net cost of testing was estimated to be A$218 000 per 100 000 infants. Medical costs incurred by the intervention group exceeded those for the control group by A$131 000 per 100 000 infants. The number of life-years saved per 100 000 infants screened was 32.378 life-years per 100 000 infants through an expected mortality rate reduction of 0.738 deaths per 100 000 infants. The cost per death averted was estimated to be A$472 913 and the cost per life-year saved was estimated to be A$10 779, which compare favorably with existing cost-effectiveness standards. This conclusion is particularly robust because conservative assumptions were made throughout, because of data limitations. Sensitivity analyses suggested that this result was relatively robust to adjustment of model parameters.

CONCLUSIONS

Tandem mass spectrometry screening for conditions caused by rare errors of metabolism is likely to be a cost-effective intervention in Australia.

Biochemical correction of very long-chain acyl-CoA dehydrogenase deficiency following adeno-associated virus gene therapy

We report the development of a gene replacement strategy for very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency. VLCAD is a mitochondrial enzyme involved in fatty acid beta-oxidation, a key step in energy production during times of fasting or stress. Deficiency of VLCAD classically presents as hepatic dysfunction, hypoglycemia, cardiomyopathy, rhabdomyolysis, and/or sudden death. While dietary therapy for VLCAD deficiency has proven beneficial in preventing some symptoms, a risk of metabolic catastrophic decompensation remains throughout life during times of increased energy demand. We designed a recombinant adeno-associated virus (AAV) expressing the human VLCAD gene (AAV8-hVLCAD). To demonstrate its in vivo activity, AAV8-hVLCAD was administered via the tail vein to VLCAD-knockout mice. A reduction in accumulated serum long-chain acylcarnitines and increased fasting tolerance judged on blood glucose concentrations were observed as of 11 days postinjections through >100 days. Western analysis of liver, skeletal muscle, and heart extracts using PEP1 anti-hVLCAD antibody revealed short-term hVLCAD expression in the liver and muscle and longer-term expression in heart. This demonstrates the ability of human VLCAD to correct the biochemical phenotype of VLCAD-deficient mice.

Development of a new enzymatic diagnosis method for very-long-chain Acyl-CoA dehydrogenase deficiency by detecting 2-hexadecenoyl-CoA production and its application in tandem mass spectrometry-based selective screening and newborn screening in Japan

The introduction of tandem mass spectrometry (MS/MS) has made it possible to screen for very-long-chain acyl-CoA dehydrogenase (VLCAD) deficiency. To confirm the diagnosis in cases with an abnormal profile of blood acylcarnitines, we developed a new enzymatic assay method for determining dehydrogenase activity toward palmitoyl-CoA (C16:0) in lymphocytes. Using this method, the production of 2-hexadecenoyl-CoA (C16:1) by crude cell lysates can be directly quantified using high performance liquid chromatography (HPLC). We applied the assay to 7 myopathic patients, 7 hypoglycemic patients, and 2 presymptomatic newborns with elevated levels of tetradecenoylcarnitine (C14:1 AC) in blood, and found impaired VLCAD activity in all of the 7 myopathic patients and both of the 2 newborns. All of the 7 hypoglycemic patients had normal level of the enzyme activity. Results of the ACADVL gene analysis were in consistent with the enzymatic diagnosis. These results suggest that MS/MS-based screening for VLCAD deficiency using blood C14:1 AC as the indicator may show a considerably high false-positive rate in selective screening of symptomatic patients. Our practical enzymatic assay can be a useful test for the accurate diagnosis of VLCAD deficiency cases screened by MS/MS.

Newborn screening for MCAD deficiency: experience of the first three years in British Columbia, Canada

BACKGROUND

Medium Chain Acyl-CoA Dehydrogenase (MCAD) Deficiency is an autosomal recessive disorder of fatty acid oxidation, with potential fatal outcome. MCAD deficiency is diagnosed by acylcarnitine analysis on newborn screening blood spot cards by tandem mass spectrometry. Early diagnosis of MCAD and presymptomatic treatment can potentially reduce morbidity and mortality.

OBJECTIVES

To evaluate incidence, clinical outcome, biochemical and molecular phenotype of MCAD cases detected in the first three years of newborn screening in British Columbia (BC).

METHODS AND RESULTS

Medium chain length acylcarnitines, octanoylcarnitine (C8) and decanoylcarnitine (C10), were measured on newborn screening blood spot cards. Out of 121,000 live births, 17 newborns had C8 values above the screening cut-off of 0.38 umol/L. Ten newborns had elevated C8 on repeat cards and were investigated further. Both C8 and C8/C10 ratios remained abnormal in all confirmed MCAD cases. Positive predictive value of screening was 58% with no false negative results. Seven patients were homozygous for the common c.985A > G MCAD mutation and three others were compound heterozygous for the c.985A > G and a second mutation. Two novel mutations were identified (c.260T > C and c.382T > A). The estimated incidence of MCAD was approximately 1:12,000 live births. Upon frequent feeding and carnitine supplementation, none of the patients had metabolic crises or adverse outcomes.

CONCLUSION

Frequency of MCAD in BC is comparable to reports from other newborn screening programs. Persistence of elevated C8 levels and C8/C10 ratios in confirmed MCAD cases suggest that these are sensitive markers for newborn screening. Early detection and treatment have successfully prevented adverse health outcomes in patients with MCAD.

Induction of oxidative stress by the metabolites accumulating in isovaleric acidemia in brain cortex of young rats

The present work investigated the in vitro effects of isovaleric acid (IVA) and isovalerylglycine (IVG), which accumulate in isovaleric acidemia (IVAcidemia), on important parameters of oxidative stress in supernatants and mitochondrial preparations from brain of 30-day-old rats. IVG, but not IVA, significantly increased TBA-RS and chemiluminescence values in cortical supernatants. Furthermore, the addition of free radical scavengers fully prevented IVG-induced increase of TBA-RS. IVG also decreased GSH concentrations, whereas IVA did not modify this parameter in brain supernatants. Furthermore, IVG did not alter lipid peroxidation or GSH concentrations in mitochondrial preparations, indicating that the generation of oxidants by IVG was dependent on cytosolic mechanisms. On the other hand, IVA significantly induced carbonyl formation both in supernatants and purified mitochondrial preparations from rat brain, with no effect observed for IVG. Therefore, it is presumed that oxidative damage may be at least in part involved in the pathophysiology of the neuropathology of IVAcidemia.

Short-chain acyl-CoA dehydrogenase (SCAD) deficiency: an examination of the medical and neurodevelopmental characteristics of 14 cases identified through newborn screening or clinical symptoms

The medical and neurodevelopmental characteristics of 14 children with short-chain acyl-CoA dehydrogenase deficiency (SCADD) are described. Eight were detected as neonates by newborn screening. Three children diagnosed on the basis of clinical symptoms had normal newborn screening results while three were born in states that did not screen for SCADD. Treatment included frequent feedings and a low fat diet. All children identified by newborn screening demonstrated medical and neuropsychological development within the normative range on follow-up, although one child had a relative weakness in the motor area and another child exhibited mild speech delay. Of the three clinically identified children with newborn screening results below the cut-off value, two were healthy and performed within the normal range on cognitive and motor tests at follow-up. Four clinically identified children with SCADD experienced persistent symptoms and/or developmental delay. However, in each of these cases, there were supplementary or alternative explanations for medical and neuropsychological deficits. Results indicated no genotype-phenotype correlations. These findings suggest that SCADD might be benign and the clinical symptoms ascribed to SCADD reflective of ascertainment bias or that early identification and treatment prevented complications that may have occurred due to interaction between genetic susceptibility and other genetic factors or environmental stressors.

Role of polyunsaturated fatty acids in the management of Egyptian children with autism

OBJECTIVE

Estimation of free polyunsaturated fatty acids (PUFAs) in blood and evaluation of behavior of autistic children before and after taking fish oil (Efalex) were performed.

DESIGN AND METHODS

30 autistic children (18 males and 12 females) aged 3-11 years and 30 healthy children as control group were included in this study. Tandem mass spectrometry and CARS were used to estimate the free PUFAs from dried blood spot and to evaluate the autistic behavior respectively.

RESULTS

Before taking Efalex, linolenic acid showed a significant reduction (71%), followed by docosahexaenoic acid (65%) and arachidonic acid (45%), while linoleic acid was the least affected PUFA (32%). After taking Efalex, 66% of autistic children showed clinical and biochemical improvement, linolenic acid and docosahexaenoic acid showed the highest levels after Efalex supplementation.

CONCLUSION

PUFA supplementation may play an important role in ameliorating the autistic behavior.

Newborn screening for methylmalonic acidurias--optimization by statistical parameter combination

With the introduction of tandem mass spectrometry, newborn screening for disorders of propionate metabolism became widely available. However, there is controversy whether population screening for these disorders should be performed. The most widely used primary metabolite C(3) itself has a poor specificity or lacks 100% sensitivity for milder forms and/or defects of cobalamin metabolism. Strategies to improve specificity have included the calculation of metabolite ratios (e.g. C(3)/C(2)) or second-tier strategies with analysis of methylmalonic acid or 2-methylcitric acid from the primary screening specimen. We report the results of a new statistical approach to identify parameter combinations that allow for 100% sensitivity as well as increased specificity. The promising results of this alternative approach will have to be substantiated on larger data sets.

Novel mutations causing medium chain acyl-CoA dehydrogenase deficiency: under-representation of the common c.985 A > G mutation in the New York state population

Medium chain acyl-CoA dehydrogenase deficiency (MCADD) is one of the most common fatty acid oxidation disorders. A subpopulation of children with MCADD present with metabolic crisis induced by fasting or illness, become lethargic, and can experience seizures or coma, culminating in a 20% mortality rate during the first episode. The frequency of these metabolic crises can be reduced with early diagnosis and treatment. The prevalence of MCADD in the United States is estimated to be 1 per 15,000 with p.K304E (c.985A > G) accounting for 90% of mutant alleles. In an 18-month period after initiating screening, the New York State Newborn Screening Mass Spectrometry Laboratory screened 385,893 newborns and referred 511 samples with elevated (>or=0.3 micromol/L) octanoylcarnitine (C8) levels for molecular testing. Of these referrals, six p.K304E homozygotes and 154 heterozygotes were identified. Twenty infants were biochemically confirmed with MCADD, per report from the child's pediatrician and/or treatment center. In these 20 cases, p.K304E accounted for only 47.5% of the mutant alleles. Further testing showed a second variant, p.Y42H, accounted for 7.5% of mutant alleles while the remaining 45% were unknown. Samples from all diagnosed non-p.K304E homozygous infants, and samples with C8 levels >or=1.0 micromol/L were sequenced (n = 16). Six novel and seven previously reported mutations were detected. These results suggest that p.K304E has a far lower representation in New York newborns with MCADD than current literature estimates and its full mutational spectrum is still unknown.

Spectrum of medium-chain acyl-CoA dehydrogenase deficiency detected by newborn screening

OBJECTIVE

Our goal was to describe the clinical spectrum of medium-chain acyl-CoA dehydrogenase deficiency detected by routine newborn screening and assess factors associated with elevations of octanoylcarnitine in newborns and characteristics associated with adverse clinical consequences of medium-chain acyl-CoA dehydrogenase deficiency.

METHODS

The first 47 medium-chain acyl-CoA dehydrogenase deficiency cases detected by the New England Newborn Screening Program were classified according to initial and follow-up octanoylcarnitine values, octanoylcarnitine-decanoylcarnitine ratios, medium-chain acyl-CoA dehydrogenase genotype, follow-up biochemical parameters, and feeding by breast milk or formula.

RESULTS

All 20 patients who were homozygous for 985A-->G had high initial octanoylcarnitine values (7.0-36.8 microM) and octanoylcarnitine-decanoylcarnitine ratios (7.0-14.5), whereas the 27 patients with 0 to 1 copy of 985A-->G exhibited a wide range of octanoylcarnitine values (0.5-28.6 microM) and octanoylcarnitine-decanoylcarnitine ratios (0.8-12.7). Initial newborn octanoylcarnitine values decreased by days 5 to 8, but the octanoylcarnitine-decanoylcarnitine ratio generally remained stable. Among 985A-->G homozygotes, breastfed newborns had higher initial octanoylcarnitine values than newborns who received formula. Adverse events occurred in 5 children, 4 985A-->G homozygotes and 1 compound heterozygote with a very high initial octanoylcarnitine: 2 survived severe neonatal hypoglycemia, 1 survived a severe hypoglycemic episode at 15 months of age, and 2 died as a result of medium-chain acyl-CoA dehydrogenase deficiency at ages 11 and 33 months.

CONCLUSION

Newborn screening for medium-chain acyl-CoA dehydrogenase deficiency has detected cases with a wide range of genotypes and biochemical abnormalities. Although most children do well, adverse outcomes have not been entirely avoided. Assessment of potential risk and determination of appropriate treatment remain a challenge.

Metabolomics reveals unique and shared metabolic changes in response to heat shock, freezing and desiccation in the Antarctic midge, Belgica antarctica

The midge, Belgica antarctica Jacobs, is subjected to numerous environmental stressors during its 2-year life cycle on the Antarctic Peninsula, and in response it has evolved a suite of behavioral, physiological, and life-cycle modifications to counter these stressors, but thus far only a limited number of biochemical adaptations have been identified. In this study, we use a metabolomics approach to obtain a broad overview of changes in energy metabolism, amino acids, and polyols in response to three of the midge's major stresses: heat, freezing, and desiccation. Using GC-MS analysis, a total of 75 compounds were identified. Desiccation (50% water loss) elicited the greatest physiological response (as determined by principal components analysis) when compared to untreated controls, with many elevated metabolites from pathways of central carbohydrate metabolism and a decrease in free amino acids. When larvae were frozen (6h at -10 degrees C), alanine and aspartate increased as well as urea. Freezing also increased three polyols (glycerol, mannitol, erythritol), while desiccation increased only two polyols (glycerol, erythritol). Heating the midges for 1h at 30 degrees C elevated alpha-ketoglutarate and putrescine while suppressing glycerol, glucose, and serine levels. Freezing and desiccation elicited elevation of four shared metabolites, whereas no shared metabolites were elevated by heat. All three treatments resulted in a reduction in serine, potentially identifying this amino acid as a marker for stress in this species. A number of metabolic changes, especially those in the sugar and polyol pools, are adaptations that have potential to enhance survival during both cold and desiccation.

[Advances in the diagnosis and treatment of maple syrup urine disease: experience in Galicia (Spain)]

INTRODUCTION

Maple syrup urine disease (MSUD) is a rare autosomal recessive disorder caused by an inherited deficiency of branched chain alpha-ketoacid dehydrogenase activity. Accumulation of the amino acids leucine, isoleucine, valine and alloisoleucine and their metabolic products in cells and biological fluids results in severe brain dysfunction.

PATIENTS AND METHODS

We present three cases of MSUD diagnosed in Galicia since 2000, the year in which the Extended Newborn Screening Program by tandem mass spectrometry was started in this region. One of the patients was diagnosed on the basis of early clinical presentation and the others by neonatal screening. Enzymatic and molecular studies confirmed two classic cases of MSUD and an intermediate variant. We describe the clinical and biochemical details at confirmation of diagnosis and the long-term outcome of the three patients. Throughout follow-up, all the patients maintained adequate leucine levels, which were near the normal range (mean levels: 220, 177 and 252 micromol/L, respectively). Several moderate metabolic decompensations were observed but leucine levels only occasionally exceeded 1000 micromol/L (one day in two patients). IQ tests were performed in all patients and scores were within the normal range. In view of our results, we believe the following measures are essential to improve the prognosis of MSUD: inclusion of this disease in Expanded Neonatal Screening Programs with early samples (at 2-3 days of life); aggressive treatment in the initial phase and during acute decompensations; strict metabolic control to prevent crises, monitoring of branched-chain amino acids (dried blood spot sample), and maintenance of long term plasma leucine levels below 300 micromol/L.

Neonatal screening for medium-chain acyl-CoA dehydrogenase (MCAD) deficiency in The Netherlands: the importance of enzyme analysis to ascertain true MCAD deficiency

The outcome was determined of population-wide neonatal screening for medium-chain acyl-CoA dehydrogenase (MCAD) deficiency using tandem mass spectrometry (MS/MS) in The Netherlands, between October 2003 and September 2005. Prospective population-wide neonatal screening for MCAD deficiency was performed in the northern part of The Netherlands. In newborns with blood octanoylcarnitine (C(8:0)) concentrations > or =0.3 micromol/L, clinical and laboratory follow-up was initiated, including MCAD enzymatic measurements which played a decisive role. In a 2-year period, 66 216 newborns were investigated for MCAD deficiency and follow-up was initiated in 28 newborns. True-positives (n = 14) were identified based upon MCAD enzyme activity <50%, measured with hexanoyl-CoA as substrate. The observed prevalence of MCAD deficiency was 1/6600 (95% CI: 1/4100-1/17 400). In addition to an elevated C(8:0) concentration, a C(8:0)/C(10:0) molar ratio >5.0 turned out to differentiate between false-positives and true-positives. Measurement of MCAD activity using phenylpropionyl-CoA as a substrate further discriminated between newborns with MCAD deficiency and so-called mild MCAD deficiency. To summarize, neonatal screening for MCAD deficiency in the northern part of The Netherlands resulted in the predicted number of affected newborns. Measurement of MCAD activity in leukocytes or lymphocytes using phenylpropionyl-CoA as a substrate can be regarded as the gold standard to diagnose MCAD deficiency upon initial positive screening test results.

The inclusion of succinylacetone as marker for tyrosinemia type I in expanded newborn screening programs

In expanded newborn screening programs by liquid chromatography/tandem mass spectrometry false negatives for tyrosinemia type I are a significant problem. We describe a method for inclusion of succinylacetone in order to avoid false negatives. We studied spots from 13,000 neonates born in Tuscany (January-May 2007) and ten spots from six patients with tyrosinemia type I. The traditional screening method was modified by adding dioxooctanoid acid (or 13C2-succinylacetone) as an internal standard to the methanolic solution of deuterated acylcarnitines and amino acids. A hydrazine solution was added to the mixture. The times of extraction, butylation and drying were only slightly prolonged. Specific multiple reaction monitoring for derivatized and labelled succinylacetone and dioxooctanoic acid was carried out. The assays were linear up to 100 micromol/L for succinylacetone. Intra- and inter-day imprecision data were in the range of 1.34% to 7.09% and 3.50% to 4.49%. Limits of detection and of quantification were 0.2 micromol/L and 0.4 micromol/L, respectively. Recovery ranged from 97.02% to 100.29%. Succinylacetone levels in samples from unaffected neonates were very close to the detection limit. Of the 46 recalls, eight (17.4%) were for abnormal tyrosine levels and all these cases had succinylacetone levels within the normal range (<2.4 micromol/L). In ten spots from six affected patients succinylacetone values ranged from 3.3 to 35.0 micromol/L. Including succinylacetone in newborn screening programs for amino acids and acylcarnitines avoids false-negative results for tyrosinemia type I. Newborn screening laboratories should consider implementing these modifications.

Determination of 3-hydroxyisovalerylcarnitine and other acylcarnitine levels using liquid chromatography-tandem mass spectrometry in serum and urine of a patient with multiple carboxylase deficiency

Due to its increased concentration in blood, 3-hydroxyisovalerylcarnitine (C5OH-I) is an important indicator for the diagnosis of organic acidemias in newborns. However, C5OH-I has not been used as a standard in tandem mass spectrometric (MS/MS) assays because its isolation is difficult. We developed a new synthesis of C5OH-I and investigated its behavior by MS/MS. A method using the multiple reaction monitoring (MRM) mode of MS/MS with HPLC was developed which provides high accuracy, precision and reproducibility. Acylcarnitine profiles in the serum and urine of a patient with multiple carboxylase deficiency (MCD) showed increased levels compared to a healthy patient.

Post-mortem analysis for two prevalent beta-oxidation mutations in sudden infant death

BACKGROUND

Fatty acid oxidation disorders may cause sudden and unexpected infant death and are associated with the histological hallmark of hepatic steatosis. The goal of the present study was to assess the value of post-mortem molecular analysis for medium-chain acyl-coenzyme A dehydrogenase (MCAD) and mitochondrial trifunctional protein (MTP) defects in unexplained sudden infant death (SID) associated with fatty infiltration of the liver. MCAD catalyzes the first step of medium-chain fatty acid oxidation while MTP catalyzes the last three steps of long-chain fatty acid oxidation.

METHODS

In a retrospective study, 220 consecutive cases of sudden and unexplained infant death certified by medical examiners at Wake Forest University Medical Center were assessed for hepatic steatosis. Subjects with evidence of hepatic steatosis were screened for mutations in MCAD and MTPalpha-subunit using DNA isolated from paraffin-embedded liver tissue, single-strand conformation variance, and nucleotide sequence analyses.

RESULTS

Sixteen cases (7.3%) were associated with diffuse micro-vesicular or mixed micro- and macro-vesicular hepatic steatosis. Two of these 16 cases (12.5%) had disease-causing mutations. One was homozygous for the prevalent MCAD A985G mutation. The second was a compound heterozygous for the prevalent MTP G1528C mutation and a novel 1 bp deletion in exon 18 of the MTPalpha-subunit gene.

CONCLUSIONS

A significant proportion (7.3%) of SID is associated with hepatic steatosis. The present data support post-mortem molecular analysis for the MCAD A985G and MTP G1528C prevalent mutations in cases of sudden and unexplained infant death associated with hepatic steatosis.

[Rare metabolic diseases]

Rare metabolic diseases are chronic, progressive, present frequently with a life-threatening course and may result in severe handicaps. They demand high diagnostic and therapeutic standards and efforts from physicians and patients. The challenge for society and health systems in dealing with patients affected by one of these diseases is to offer comprehensive service by a multi-professional team of specialists and evidence-based as well as economic (i.e. necessary, sufficient and effective) treatment. Patients and families should be treated in specialized metabolic centres guaranteeing continuous improvement of the scientific and clinical principles of treatment, standardized outcome evaluation, strict quality assurance as well as optimal psychosocial care and counselling. Networking of national and international metabolic centres seems imperative for clinical research in the field of rare metabolic diseases in order to provide adequate sample sizes and to yield substantial results.

Critical sample pretreatment in monitoring dried blood spot citrulline

BACKGROUND

Plasma Citrulline concentration has been correlated to functional enterocyte mass. Dried blood spot (DBS) analysis using LC-MSMS reduces sample amount needed. We optimized DBS elution to increase precision and accuracy of DBS LC-MSMS analysis.

METHOD

DBS control samples were eluted in varying pH (2.2-7.0) and for varying times (15-75 min) and Cit, Arg and Orn were analyzed using LC-MSMS, with and without derivatization. In 20 volunteers, the DBS LC-MSMS assay was correlated with a plasma ion exchange HPLC method.

RESULTS

For Citrulline an extraction optimum was obtained at pH 2.6, whereas lower Arginine concentrations were found using low extraction pH. Increasing elution times lead to increased concentrations. Within-run CV was higher with, compared to without derivatization. No close association could be found between plasma HPLC and DBS LC-MSMS concentrations.

CONCLUSION

Analysis of amino acids on DBS using LC-MSMS should be optimized regarding the purpose of the assay. In our study, most optimal results were obtained without derivatization and elution in pH 2.6 for 45 min. Cellular amino acids in DBS might influence the correlation of Cit with severity of enteral disorders. Therefore, further evaluation of DBS Cit as a marker for enteral disorders is warranted.

Clinical characteristics of neonates with inborn errors of metabolism detected by Tandem MS analysis in Oman

We reviewed the clinical profile of our neonates diagnosed to have inborn errors of metabolism (IEM) by Tandem Mass Spectrometry (TMS) over a seven years period, and compared the results with published reports. We also attempted to evaluate various clinical situations wherein the screening test would yield a high pick up rate. Among the 166 neonates studied (10 aged 1 day, 79 aged 2-7 days and 77 aged 8-28 days), significant abnormalities on TMS suggestive of IEM were detected in 38 babies (23%), most common diseases diagnosed were maple syrup urine disease (10 neonates), propionic acidemia (8 neonates), urea cycle diseases (6 neonates) and isovaleric acidemia (4 neonates). The detection incidence was calculated to be one positive case out of every 4 to 5 babies tested. A high prevalence of parental consanguinity and high level of positive family history of affected siblings were the highlights of this study. The major clinical situations where testing was helpful were (a) unexplained acute neonatal encephalopathy, (b) positive family history of known or suspected IEM and (c) new born presenting with abnormal serum biochemistry suggestive of IEM.

Selective screening for inborn errors of metabolism on clinical patients using tandem mass spectrometry in China: a four-year report

We have initiated clinical selective screening for inborn errors of metabolism in China by analysing amino acids and acylcarnitines in a dried blood filter-paper samples using tandem mass spectrometry. Samples from a total of 3070 children suspected of inborn errors of metabolism were collected through a study network which covered most provinces of China. The diagnoses were further confirmed through clinical symptoms, by gas chromatography-mass spectrometry and other biochemistry studies, and in a few cases by DNA analysis. In all, 212 cases were diagnosed (6.6%) including 92 (43.4%) with amino acids disorders (48 with phenylketonuria, 12 with ornithine carbamoyltransferase deficiency, 7 with tyrosinaemia type I, 9 with maple syrup urine disease, 5 with citrullinaemia type I, 8 with citrullinaemia type II, 2 with homocystinuria, and 1 with argininaemia); 107 (50.5%) with organic acid disorders (including 58 with methylmalonic acidaemia, 13 with propionic acidaemia, 6 with isovaleric acidaemia, 7 with glutaric acidaemia type I, 6 with 3-methylcrotonyl-CoA carboxylase deficiency, 2 with 3-hydroxy-3-methylglutaryl-CoA lyase deficiency, 10 with multiple carboxylase deficiency, and 5 with beta-ketothiolase deficiency); and 13 (6.1%) with fatty acid oxidation disorders (including 1 with carnitine palmitoyltransferase deficiency type I, 1 with carnitine palmitoyltransferase deficiency type II, 1 with short-chain acyl-CoA dehydrogenase deficiency, 5 with medium-chain acyl-CoA dehydrogenase deficiency, 3 with very long-chain acyl-CoA dehydrogenase deficiency, and 2 with multiple acyl-CoA dehydrogenase deficiency). It is suggested that tandem mass spectrometry is useful for selective screening of clinically suspected patients. The majority of diseases (94%) in this study were amino acid disorders and organic acid disorders. Fatty acid oxidation disorders are relatively rare in the Chinese, but medium-chain acyl-CoA dehydrogenase deficiency should be further investigated.

Policy issues related to expanded newborn screening: a review of three genetic/metabolic disorders

In 2005, a federal advisory committee recommended that the number of disorders in state newborn screening programs be expanded from 9 to 29. In view of this recommendation, state leaders will need to make cogent decisions regarding the expanse of their state newborn screening programs. They must consider several factors, including the costs and outcomes of the screening program. The expense of the initial screening test can be misleading because it does not include the cost of the entire program (testing, tracking, notifying, retesting, confirmatory testing, and follow-up). Also, outcomes such as false positive findings can be costly to newborn screening programs, result in additional testing for infants, and lead to parental concern and worry. This article examines some of the policy issues related to newborn screening and specifically focuses on three disorders recommended for newborn screening, cystic fibrosis (CF), medium-chain acyl CoA dehydrogenase Deficiency (MCADD), and beta-ketothiolase (BKT).

Cost-effectiveness of neonatal screening for medium chain acyl-CoA dehydrogenase deficiency: the homogeneous population of The Netherlands

OBJECTIVE

To assess the cost-effectiveness of neonatal screening on medium chain acyl-CoA dehydrogenase (MCAD) deficiency in a homogeneous population.

STUDY DESIGN

For the scenario without neonatal screening, medical chart review and interviews were performed with physicians and families of 116 Dutch patients born between 1985 and July 2003 with clinically ascertained MCAD deficiency. For the scenario with neonatal screening, 66,205 unaffected and 11 affected newborns identified by prospective neonatal screening for MCAD deficiency in the northern part of the Netherlands were evaluated. The incremental cost-effectiveness ratio (ICER) used life years (LYs) as the outcome measure by combining both scenarios in a decision model with second-order Monte Carlo simulation.

RESULTS

For the scenarios with and without neonatal screening for MCAD deficiency, costs were $6.10 and $4.22 per newborn, respectively. The main cost categories were institutionalization (64%), admissions (17%), special education (8%), laboratory testing (4%), and (para)medical contact (4%). The resulting ICER was $1653 per LY gained. Sensitivity analysis generated an ICER between $14,839 and $4345 per LY gained.

CONCLUSIONS

Screening for MCAD deficiency in a well-defined population generates an ICER well within accepted boundaries for cost-effective interventions, even after sensitivity analysis.

Carnitine, acylcarnitine and amino acid profiles analyzed by tandem mass spectrometry in a surfactant/virus mouse model of acute hepatic encephalopathy

Tandem mass spectrometry (MS/MS) was used to analyze multiple serum metabolites for the first time in a surfactant/virus mouse model of acute hepatic encephalopathy (AHE). AHE is characterized by acute liver failure that can lead to potentially lethal increases in intracranial pressure. We have reproduced AHE in young CD-1 mice exposed from postnatal day (P) 2-13 to the industrial surfactant, Toximul 3409F (Tox), and then infected intranasally on P14 with sublethal doses (LD(10-30)) of mouse-adapted human influenza B (Lee) virus (FluB). The sera analyzed by MS/MS were from mice exhibiting typical markers of Tox-mediated potentiation of viral illness, including reduced weights and blood glucose levels. Most metabolite abnormalities were not evident until five days after viral infection (P19), the time corresponding to the onset of weight loss and mortality. Values for fatty acylcarnitines and amino acids in the Tox+FluB-treated mice were either additive or supra-additive relative to the effects of either treatment alone. Amino acid profiles were consistent with those reported for human AHE. None of the treated mice exhibited signs of carnitine deficiency, and propionylcarnitine levels were normal. On P19, mice given combined Tox+FluB treatment had significant increases in levels of both medium- and long-chain acylcarnitines (C6:0-C12:0 and C14:0-C20:0, respectively), including their monounsaturated metabolites. Levels of medium-chain dicarboxylic and long-chain hydroxy-acylcarnitines were also elevated in the combined treatment group. The results of this study indicate a diffuse mitochondrial dysfunction in Tox+FluB-treated mice that results in a serum metabolite profile unique from those observed in classic inherited metabolic disorders.