Validity and reliability of the MetabQoL 1.0 and assessment of neuropsychiatric burden in organic acidemias: Reflections from Turkey.

OBJECTIVES: The MetabQoL 1.0 is the first disease-specific health related quality of life (HrQoL) questionnaire for patients with intoxication-type inherited metabolic disorders. Our aim was to assess the validity and reliability of the MetabQoL 1.0, and to investigate neuropsychiatric burden in our patient population. METHODS: Data from 29 patients followed at a single center, aged between 8 and 18 years with the diagnosis of methylmalonic acidemia (MMA), propionic acidemia (PA) or isovaleric acidemia (IVA), and their parents were included. The Pediatric Quality of Life Inventory (PedsQoL) was used to evaluate the validity and reliability of MetabQoL 1.0. RESULTS: The MetabQoL 1.0 was shown to be valid and reliable (Cronbach's alpha: 0.64-0.9). Fourteen out of the 22 patients (63.6%) formally evaluated had neurological findings. Of note, 17 out of 20 patients (85%) had a psychiatric disorder when evaluated formally by a child and adolescent psychiatrist. The median mental scores of the MetabQoL 1.0 proxy report were significantly higher than those of the self report (p = 0.023). Patients with neonatal-onset disease had higher MetabQoL 1.0 proxy physical (p = 0.008), mental (p = 0.042), total scores (p = 0.022); and self report social (p = 0.007) and total scores (p = 0.043) than those with later onset disease. CONCLUSIONS: This study continues to prove that the MetabQoL 1.0 is an effective tool to measure what matters in intoxication-type inherited metabolic disorders. Our results highlight the importance of clinical assessment complemented by patient reported outcomes which further expands the evaluation toolbox of inherited metabolic diseases.

An Economic Evaluation of Neonatal Screening for Inborn Errors of Metabolism Using Tandem Mass Spectrometry in Thailand.

BACKGROUND: Inborn errors of metabolism (IEM) are a rare group of genetic diseases which can lead to several serious long-term complications in newborns. In order to address these issues as early as possible, a process called tandem mass spectrometry (MS/MS) can be used as it allows for rapid and simultaneous detection of the diseases. This analysis was performed to determine whether newborn screening by MS/MS is cost-effective in Thailand. METHOD: A cost-utility analysis comprising a decision-tree and Markov model was used to estimate the cost in Thai baht (THB) and health outcomes in life-years (LYs) and quality-adjusted life year (QALYs) presented as an incremental cost-effectiveness ratio (ICER). The results were also adjusted to international dollars (I$) using purchasing power parities (PPP) (1 I$ = 17.79 THB for the year 2013). The comparisons were between 1) an expanded neonatal screening programme using MS/MS screening for six prioritised diseases: phenylketonuria (PKU); isovaleric acidemia (IVA); methylmalonic acidemia (MMA); propionic acidemia (PA); maple syrup urine disease (MSUD); and multiple carboxylase deficiency (MCD); and 2) the current practice that is existing PKU screening. A comparison of the outcome and cost of treatment before and after clinical presentations were also analysed to illustrate the potential benefit of early treatment for affected children. A budget impact analysis was conducted to illustrate the cost of implementing the programme for 10 years. RESULTS: The ICER of neonatal screening using MS/MS amounted to 1,043,331 THB per QALY gained (58,647 I$ per QALY gained). The potential benefits of early detection compared with late detection yielded significant results for PKU, IVA, MSUD, and MCD patients. The budget impact analysis indicated that the implementation cost of the programme was expected at approximately 2,700 million THB (152 million I$) over 10 years. CONCLUSION: At the current ceiling threshold, neonatal screening using MS/MS in the Thai context is not cost-effective. However, the treatment of patients who were detected early for PKU, IVA, MSUD, and MCD, are considered favourable. The budget impact analysis suggests that the implementation of the programme will incur considerable expenses under limited resources. A long-term epidemiological study on the incidence of IEM in Thailand is strongly recommended to ascertain the magnitude of problem.

Cost-effectiveness of liver transplantation in methylmalonic and propionic acidemias.

Propionic acidemia (PA) and classical methylmalonic acidemia (MMA) are rare inborn errors of metabolism that can cause early mortality and significant morbidity. The mainstay of disease management is lifelong protein restriction. As an alternative, liver transplantation (LT) may improve survival, quality of life, and prevent further neurological deterioration. The aim of our study was to estimate the incremental costs and outcomes of LT versus nutritional support in patients with early-onset MMA or PA. We constructed a Markov model to simulate and compare life expectancies, quality-adjusted life years (QALYs), and lifetime direct and indirect costs for a cohort of newborns with MMA or PA who could either receive LT or be maintained on conventional nutritional support. We conducted a series of 1-way and probabilistic sensitivity analyses. In the base case, LT on average resulted in 1.5 more life years lived, 7.9 more QALYs, and a savings of $582,369 for lifetime societal cost per individual compared to nutritional support. LT remained more effective and less costly in all 1-way sensitivity analyses. In the probabilistic sensitivity analysis, LT was cost-effective at the $100,000/QALY threshold in more than 90% of the simulations and cost-saving in over half of the simulations. LT is likely a dominant treatment strategy compared to nutritional support in newborns with classical MMA or PA.

Newborn screening by tandem mass spectrometry for glutaric aciduria type 1: a cost-effectiveness analysis.

BACKGROUND: Glutaric aciduria type I (GA-I) is a rare metabolic disorder caused by inherited deficiency of glutaryl-CoA dehydrogenase. Despite high prognostic relevance of early diagnosis and start of metabolic treatment as well as an additional cost saving potential later in life, only a limited number of countries recommend newborn screening for GA-I. So far only limited data is available enabling health care decision makers to evaluate whether investing into GA-I screening represents value for money. The aim of our study was therefore to assess the cost-effectiveness of newborn screening for GA-I by tandem mass spectrometry (MS/MS) compared to a scenario where GA-I is not included in the MS/MS screening panel. METHODS: We assessed the cost-effectiveness of newborn screening for GA-I against the alternative of not including GA-I in MS/MS screening. A Markov model was developed simulating the clinical course of screened and unscreened newborns within different time horizons of 20 and 70 years. Monte Carlo simulation based probabilistic sensitivity analysis was used to determine the probability of GA-I screening representing a cost-effective therapeutic strategy. RESULTS: Within a 20 year time horizon, GA-I screening averts approximately 3.7 DALYs (95% CI 2.9 - 4.5) and about one life year is gained (95% CI 0.7 - 1.4) per 100,000 neonates screened initially . Moreover, the screening programme saves a total of around 30,682 Euro (95% CI 14,343 to 49,176 Euro) per 100,000 screened neonates over a 20 year time horizon. CONCLUSION: Within the limitations of the present study, extending pre-existing MS/MS newborn screening programmes by GA-I represents a highly cost-effective diagnostic strategy when assessed under conditions comparable to the German health care system.

Impact of inborn errors of metabolism on admission in a neonatal intensive care unit--a prospective cohort study.

OBJECTIVE: To estimate the incidence of Inborn errors of metobolism (IEM) in Neonatal intensive care unit (NICU) using tandem mass spectrometry and to determine the impact that these disorders have on NICU resources. METHODS: During the period of study, 724 (81% eligible cases) dried blood filter-paper samples were collected from a NICU. The samples were analysed using tandem mass spectrometry. The diagnosis was further confirmed through clinical symptoms and by gas chromatography-mass spectrometry. The results were also confirmed by clinical follow-up of all positive patients in an overall interval of 1 year. The mean observation period was 11 months per neonate. RESULTS: In total, 22 cases were screen positive and 8 cases of inborn errors of metabolism were detected. The incidence of IEM in the population of patients admitted to the authors' NICU was 1.1%. The most common inborn error found was methylmalonic acidemia (3 cases, 37.5%), and all of the cases needed aggressive treatment and invasive mechanical ventilation. There were two cases of Tyrosinemia type 1, one case each of Maple Syrup Urine Disease, Propionic Acidemia, and Multiple Acyl-CoA dehydrogenase deficiency (MADD). Five of the eight patients required invasive mechanical ventilation. The median length of NICU stay was 3 days (1~7 days) and early therapeutic intervention was effective for four of them and other four patients (50%) died. CONCLUSIONS: The incidence of IEM in NICU was 1.1%, indicating an underestimation of the incidence of metabolic disorders prior to implementing screening. Most patients with IEM in the NICU required invasive mechanical ventilation and the mortality was increased due to underlying IEM.

Extended newborn screening: an update for the general paediatrician.

Extended newborn screening (ENBS) with the use of tandem mass spectrometry technology is well established in all Australian states and in New Zealand. ENBS has afforded a marked reduction in morbidity and mortality in select conditions such as medium-chain acyl-CoA dehydrogenase deficiency. While this technology has been of great benefit to newborn screening, it comes with many inherent and unforeseen challenges. In this review, we discuss the successes and challenges associated with ENBS.

Long-term needs of adult patients with organic acidaemias: outcome and prognostic factors.

BACKGROUND: With improvements in the treatment of children with organic acidaemias (OA), the number surviving to adulthood is increasing. To plan appropriate services for their care it is important to know what their needs are. OBJECTIVE: To describe the clinical and social problems affecting adult patients with OA. PATIENTS AND METHODS: We reviewed the medical records of 15 adult patients diagnosed with OA. Social attainment (housing, schooling and occupation) was analysed. Nutritional status was evaluated by body mass index (BMI) and laboratory studies. Neurological and visceral complications were noted. Cognitive outcome was evaluated by psychometric testing and/or educational attainment. RESULTS: Seven had methylmalonic acidaemia (MMA), 4 isovaleric acidaemia (IVA) and 4 propionic acidaemia (PA). Ten were female, and median age was 23.5 years (range 18-48). All but three had late-onset disease. Two patients became pregnant during follow up. Four patients had obtained university degrees and were working. Three-quarters of the patients required some kind of social support. All had a good nutritional status. Height was normal in IVA and 3 PA patients. Osteoporosis was present in 2 out of 8 patients assessed. A variety of neurocognitive or visceral complications were seen in two-thirds of the patients. Metabolic decompensations were unusual. CONCLUSIONS: The approach to adult patients with OA has to be multidisciplinary, with the clinician and dietician as the core of the team, but with the collaboration of clinical nurses specialists, social workers and other specialist services and the support of a biochemical and molecular laboratory.

Essential fatty acid profiling for routine nutritional assessment unmasks adrenoleukodystrophy in an infant with isovaleric acidaemia.

We report a 16-month-old asymptomatic male with enzyme confirmed isovaleric acidaemia (IVA; isovaleryl-CoA dehydrogenase deficiency; OMIM 243500) who, upon routine nutritional follow-up, presented evidence of peroxisomal dysfunction. The newborn screen (2 days of life) revealed elevated C(5)-carnitine (2.95 µmol/L; cutoff <0.09 µmol/L) and IVA was subsequently confirmed by metabolic profiling and in vitro enzymology. Plasma essential fatty acid (EFA) analysis, assessed to evaluate nutritional status during protein restriction and L: -carnitine supplementation, revealed elevated C(26:0) (5.0 µmol/L; normal <1.3). Subsequently, metabolic profiling and molecular genetic analysis confirmed X-linked adrenoleukodystrophy (XALD). Identification of co-inherited XALD with IVA in this currently asymptomatic patient holds significant treatment ramifications for the proband prior to the onset of neurological sequelae, and critically important counselling implications for this family.

Newborn screening in North Carolina: the evolution of policy and practice.

Newborn screening policies in North Carolina are due to the efforts of skilled and knowledgeable state officials, clinicians, and scientists who are able to develop effective newborn screening procedures. A newborn screening that was developed in North Carolina is the first automated method for diagnosing phenylketonuria. This process was later adopted in many other states. The use of tandem mass spectrometry in newborn screening was also pioneered in North Carolina, and it is being used in an increasing number of states. Newborn screening is more than testing, however; follow-up and specialized care are essential. State-level policies should recognize the multiple links necessary to make newborn screening effective and efficient.

Assessment of an electron-impact GC-MS method for organic acids and glycine conjugates in amniotic fluid.

We assessed the reliability of a method designed for common electron-impact GC-MS systems to determine in a single run most organic acids and glycine conjugates of clinical interest in amniotic fluid. Suitable sensitivity was achieved by dividing the selected-ion chromatogram into 12 time segments during which the monitoring dwelt on specific ions. Twelve metabolites were simultaneously quantified in amniotic fluid, with performances ranging from very good to clinically acceptable. The total coefficient of variation was 2.5-14.1% and the detection limit was well below the lower value of the physiological range. For five other metabolites, the precision was lower and/or the detection limit was near the physiological range. The method was clinically assessed by the prenatal detection of three cases of tyrosinaemia type I and one case of propionic acidaemia. Analytical and clinical evaluation of the method showed that GC-MS with electron-impact fragmentation can be an informative analytical approach for low-level organic acids in physiological fluids. Apart from the case of glycine conjugates, the method shows a fair reliability for amniotic fluid analysis, which might warrant its use for prenatal diagnosis of organic acidurias. However, this method cannot replace procedures using isotopic internal standards, nor GC-MS based on chemical ionization fragmentation, which remain confirmatory analytical methods of choice.

Evaluation of a mass screening program for lysinuric protein intolerance in the northern part of Japan.

Lysinuric protein intolerance (LPI:MIM 222700) is an autosomal recessive disease characterized by defective transport of the dibasic amino acids. We recently reported a local cluster of LPI in the northern part of Japan (Koizumi et al., 2000). Mutational analysis of the LPI patients in this local cluster revealed they were exclusively homozygous for the R410X mutation. The effectiveness of early intervention with citrulline therapy (200 mg/kg per day) and protein restriction (1.5 g/kg per day) was confirmed in these patients. Mass screening was conducted in 4,568 newborn babies between 1999 and 2002, which was estimated to cover 100% of almost all newborns delivered in the screened area. Forty heterozygous newborns were found (0.88%), leading to an estimated incidence of LPI of 1:51,984. The number of people that required screening to detect one case was 51,984, and the cost for mass screening was 30 cents/person (a total of dollars 15,600). This is comparable to, or even less than, the cost of currently screened diseases in Japan. Therefore, we conclude that a mass screening program for LPI can be introduced effectively and economically into an area where an LPI cluster is located as the result of a founder mutation.

Newborn screening--is it really that simple?

The incorporation of tandem mass spectrometry (MSMS) into an existing newborn screening program is an evolving process. Limited worldwide experience has ensured that all stages of reliability testing need to be followed. These include a literature review to establish methodology and analytes/disorders for testing and a pilot screening project including assaying archival samples from subjects with proven target disorders. Algorithms used for analyte concentrations and the relationships of various analytes to one another for resample criteria need to be continually reassessed to maximise screening specificity, sensitivity and positive predictive value. Since 1st of April 1998, the NSW Newborn Screening Program has screened 320, 848 babies using electrospray MSMS for selected amino acids and acyl camitines. Screening for amino acids has led to requests for 415 repeat samples with 94 babies referred for further testing. Of these 73 had a disorder of amino acid metabolism, including 43 with persistent hyperphenylalaninemia (36 of whom had PKU, 2 had a pterin pathway defect, 5 HPAA). Screening for acyl carnitines has led to requests for 245 repeat samples with 63 babies referred for further investigation. Of these 44 had a diagnosed disorder, including 15 with medium chain acyl CoA dehydrogenase deficiency. Five babies with confirmed disorders detectable with MS/MS had negative test results. The cost of screening using MSMS was only $A0.50 more than the method for screening for PKU and homocystinuria alone (ie the bacterial inhibition assays) and has allowed detection of an additional 74 babies at least 48 of whom have a diagnosis for which early treatment seems clearly beneficial. MSMS has shown a sensitivity of 95.9% and specificity of 99.8% in our laboratory with a positive predictive value of 18%.

Tandem mass spectrometry and newborn screening: pilot data and review.

United States legislatures are debating whether to use tandem mass spectrometry to expand the roster of inherited disorders tested in newborn screening programs. The debate is hampered because published financial data comparing charges associated with late vs early diagnosis are not readily available. We provide pilot financial data comparing late diagnosis vs presumptive diagnosis and early management taken from consecutive patients with propionic acidemia diagnosed from 1995-1998 in New Hampshire. We extrapolated from these data and the incidence of treatable inborn errors of metabolism to estimate the projected yearly savings of critical care charges if expanded newborn screening were instituted. We conclude that institution of expanded screening will bring diminished morbidity and large savings in yearly chronic care and critical care charges.

A pilot study of neonatal screening by electrospray ionization tandem mass spectrometry in Taiwan.

Amino acid and acylcarnitine profiling of dry blood specimens using electrospray tandem mass spectrometry (ESI/MS/MS) has been recognized as an useful tool for screening inherited metabolic defects of newborns. In this pilot study, we introduced this technology to screen 2100 newborns to establish the normal amino acid and acylcarnitine level. Based on the upper cutoff level (average + 4*SD), twenty-nine samples studied were considered as abnormal. After follow-up samples and urine GC/MS analysis, only two were confirmed as true inborn errors. One was identified as hyperphenylalaninemia, and the other as isovaleric acidemia. The positive rate of true inborn metabolic error was 0.09% (2/2100), and the false positive rate 1.28% (29/2100) in this study. ESI/MS/MS is proven to be an adequate tool for inborn metabolic error screening.

Inborn errors of amino acid metabolism. The best strategy for their diagnosis.

We performed a cost-effectiveness analysis to evaluate whether a pediatrician who suspects an inherited disease of amino acid metabolism should refer the child to a specialist in inborn errors of amino acid metabolism or should prescribe the usual screening test, chromatography of amino acids. Actual hospital costs were used to value the referral, the tests, and the complications that occur when the diagnosis is not recognized. The percent of confirmed diagnoses was chosen as a measure of effectiveness. We conclude that it is more cost-effective for a pediatrician to refer the child to a specialist, that the best strategy in the absence of a referral is to prescribe thin-layer chromatography, and that the least cost-effective strategy is to perform ion-exchange chromatography immediately.

Use of placental enzyme analysis in assessment of the newborn at risk for non-ketotic hyperglycinaemia (NKH).

The incidence of non-ketotic hyperglycinaemia (NKH), McKusick 23830, in the population of British Columbia, Canada was found to be the same as that reported for Finland. We present the plasma glycine levels in ten non-ketotic hyperglycinaemia patients and outline difficulties in interpreting plasma glycine levels in their newborn siblings. We propose the use of a placental glycine cleavage enzyme (EC 2.1.1.10) assay to rule out a diagnosis of non-ketotic hyperglycinaemia in at-risk infants during the first few days of life.