Clinical efficacy and cost-effectiveness of newborn screening for medium chain acyl-CoA dehydrogenase deficiency using tandem mass spectrometry

OBJECTIVE: To determine the clinical efficacy and cost-effectiveness of newborn screening for MCADD using tandem mass spectrometry (MS/MS) compared with clinical diagnosis within the Canadian context. DESIGN AND METHODS: A systematic review of the clinical and economic literature was performed. For primary economic analysis, a decision-tree model was built based on the available information, the impact of newborn screening on the health care and the relevant Canadian data. RESULTS: Twenty-one clinical and two economic studies met the selection criteria. Mean incidence of MCADD was approximately 1:16,000. Clinical sensitivity and specificity were 100% and 99.99%, respectively. Screening significantly lowered morbidity and mortality. Both economic studies showed that screening for MCADD using MS/MS was cost-effective if willingness-to-pay was US 50,000 dollars. Our primary economic analysis showed that screening was cost-effective based on the cost-effective threshold of C 20,000 dollars per QALY. CONCLUSION: Screening consumes more resources than no screening but attains better health outcomes.     

A novel method for quantitation of acylglycines in human dried blood spots by UPLC-tandem mass spectrometry

BackgroundSeveral acylcarnitines used as primary markers on dried blood filter papers (DBS) for newborn screening lack specificity and contribute to a higher false positive rate. The analysis of urine acylglycines is useful in the diagnosis of inborn errors of metabolism (IEM) including medium chain acyl-CoA dehydrogenase deficiency (MCADD), isovaleric acidemia, and beta-ketothiolase deficiency (BKTD). Currently, no method for analyzing acylglycines from DBS has been published.MethodsAcylglycines were extracted from two 3.2 mm DBS punches and butylated using Butanol-HCl. Ultra Performance Liquid Chromatography (UPLC-MS/MS) with run time of 10 min permits resolution and quantitation of 15 acylglycines; including several isobaric. Method development was completed. Reference intervals (n = 573) were established for four birth weight groups. Furthermore, samples from patients with a confirmed IEM (n = 11), and false positive screens (n = 78) were analyzed to validate the interpretation obtained from the newly established reference intervals.ResultsCalibration curves were linear from 0.005 to 25.0 μM. Ion suppression was evaluated as minimal (2 to 10%). Samples from known patients were used to validate the reference intervals. For C5OH-related disorders, tiglylglycine (TG), TG/acetylglycine (AG) ratio, 3methylcrotonylglycine (3MCG) and 3MCG/AG ratio increased specificity. Propionylglycine (PG) and PG/acetylglycine ratio were two discriminatory markers in the investigation of C3-related disorders. Hexanoylglycine (HG), octanoylglycine (OG), suberylglycine (SG), and the ratios HG/AG, OC/AG and SG/AG were excellent markers of MCADD deficiency.ConclusionThis method shows potential application as a second tier screen in order to reduce the false positive rate for a number of IEM targeted by newborn screening.     

A biochemical perspective on the use of tandem mass spectrometry for newborn screening and clinical testing

The first newborn screen was a clinical test to detect a disorder of the biochemistry of the amino acid, phenylalanine. This disorder, known as phenylketonuria, produces profound mental retardation if not detected and treated early in life. Early screening programs relied on inexpensive population screening techniques that have all but been replaced by more accurate analytical methods such as tandem mass spectrometry (MS/MS). MS/MS enables a multianalyte approach for detecting biochemical disorders such that a metabolic profile is obtained rather than a single analyte measurement. The metabolic profile has clearly shown improvements in the detection of diseases such as phenylketonuria and several new disorders arising from errors in fatty acid oxidation and organic acid metabolism. MS/MS is a powerful tool for accessing the metabolic status of a newborn and can detect both inborn metabolic errors as well as examine the effect of acquired diseases or pharmacologic intervention on intermediary metabolism.     

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).     

Use of tandem mass spectrometry for multianalyte screening of dried blood specimens from newborns

BACKGROUND: Over the past decade laboratories that test for metabolic disorders have introduced tandem mass spectrometry (MS/MS), which is more sensitive, specific, reliable, and comprehensive than traditional assays, into their newborn-screening programs. MS/MS is rapidly replacing these one-analysis, one-metabolite, one-disease classic screening techniques with a one-analysis, many-metabolites, many-diseases approach that also facilitates the ability to add new disorders to existing newborn-screening panels. METHODS: During the past few years experts have authored many valuable articles describing various approaches to newborn metabolic screening by MS/MS. We attempted to document key developments in the introduction and validation of MS/MS screening for metabolic disorders. Our approach used the perspective of the metabolite and which diseases may be present from its detection rather than a more traditional approach of describing a disease and noting which metabolites are increased when it is present. CONTENT: This review cites important historical developments in the introduction and validation of MS/MS screening for metabolic disorders. It also offers a basic technical understanding of MS/MS as it is applied to multianalyte metabolic screening and explains why MS/MS is well suited for analysis of amino acids and acylcarnitines in dried filter-paper blood specimens. It also describes amino acids and acylcarnitines as they are detected and measured by MS/MS and their significance to the identification of specific amino acid, fatty acid, and organic acid disorders. CONCLUSIONS: Multianalyte technologies such as MS/MS are suitable for newborn screening and other mass screening programs because they improve the detection of many diseases in the current screening panel while enabling expansion to disorders that are now recognized as important and need to be identified in pediatric medicine.     

Screening of newborns and high-risk group of children for inborn metabolic disorders using tandem mass spectrometry in South Korea: a three-year report

BACKGROUND: Mass screening using tandem mass spectrometry(MS/MS) was initiated to determine if the incidence of metabolic disorder is sufficiently high to meet the criteria for newborn screening, and whether or not early medical intervention might be beneficial to the patients. METHODS: Newborns and children in a high-risk group were screened using MS/MS from April 2001 to March 2004. Blood spots of newborns were collected between 48 and 72 h after birth. The dried blood spots was extracted with 150 microl of methanol, and analyzed by MS/MS. RESULTS: From April 2001 to March 2004, 79,179 newborns were screened for organic, amino and fatty acid metabolism disorders, which account for approximately 5.4% of annual births in South Korea. Twenty-eight newborns were diagnosed with one of the metabolic disorders and the collective estimated prevalence amounted to 1 in 2800 with a sensitivity of 97.67%, a specificity of 99.28%, a recall rate of 0.05%, and a positive predictive value of 6.38%. 6795 infants/children at high risk were screened and 20 were confirmed to have metabolic disorders. CONCLUSION: The collective total prevalence of 1:2800 in newborns indicates an underestimation of the incidence of metabolic disorders prior to implementing MS/MS screening in South Korea.     

Expanded newborn screening of inherited metabolic disorders by tandem mass spectrometry: clinical and laboratory aspects

Newborn screening started in the 1960s for the purpose of identifying phenylketonuric patients to begin early intervention and to prevent mental retardation in these patients. Soon thereafter, screening programs expanded to include additional genetic disorders added individually one at a time. In the 1980s, tandem mass spectrometry (MS/MS) was introduced in clinical laboratories, and in the 1990s, the technique was used for newborn screening. Unlike measuring one analyte at a time, MS/MS allows measurement of >40 analytes, in a few minutes with the use of a single assay. Currently, MS/MS is being used for the identification of several amino acid, organic acid and fatty acid disorders. Several states in the United States and many other countries are using MS/MS in newborn screening. However, there is a significant disparity among different newborn screening programs for disorders being screened by MS/MS and many other challenges are faced by the expanded newborn screening. It is anticipated that in the future the use of MS/MS in newborn screening will expand both at the analyte and geographic levels. Clinicians and laboratory scientists should become familiar with MS/MS, disorders being screened in their patients' population and the future of this emerging technology.     

Tandem mass spectrometric analysis for amino, organic, and fatty acid disorders in newborn dried blood spots: a two-year summary from the New England Newborn Screening Program.

BACKGROUND: Tandem mass spectrometry (MS/MS) is rapidly being adopted by newborn screening programs to screen dried blood spots for >20 markers of disease in a single assay. Limited information is available for setting the marker cutoffs and for the resulting positive predictive values. METHODS: We screened >160 000 newborns by MS/MS. The markers were extracted from blood spots into a methanol solution with deuterium-labeled internal standards and then were derivatized before analysis by MS/MS. Multiple reaction monitoring of each sample for the markers of interest was accomplished in approximately 1.9 min. Cutoffs for each marker were set at 6-13 SD above the population mean. RESULTS: We identified 22 babies with amino acid disorders (7 phenylketonuria, 11 hyperphenylalaninemia, 1 maple syrup urine disease, 1 hypermethioninemia, 1 arginosuccinate lyase deficiency, and 1 argininemia) and 20 infants with fatty and organic acid disorders (10 medium-chain acyl-CoA dehydrogenase deficiencies, 5 presumptive short-chain acyl-CoA dehydrogenase deficiencies, 2 propionic acidemias, 1 carnitine palmitoyltransferase II deficiency, 1 methylcrotonyl-CoA carboxylase deficiency, and 1 presumptive very-long chain acyl-CoA dehydrogenase deficiency). Approximately 0.3% of all newborns screened were flagged for either amino acid or acylcarnitine markers; approximately one-half of all the flagged infants were from the 5% of newborns who required neonatal intensive care or had birth weights <1500 g. CONCLUSIONS: In screening for 23 metabolic disorders by MS/MS, an mean positive predictive value of 8% can be achieved when using cutoffs for individual markers determined empirically on newborns.     

Newborn screening for metabolic diseases: Saving children's lives and improving outcomes

Newborn screening for metabolic diseases was initially introduced in the 1960s with a program for the early diagnosis of phenylketonuria. Guidelines for the introduction of additional conditions to the screen required that the condition was sufficiently common to merit screening, that it was treatable and that the cost of diagnosis was not prohibitive. Additional conditions added to the screen included congenital hypothyroidism and congenital adrenal hyperplasia. The recognition of medium-chain acyl0CoA dehydrogenase deficiency coupled to the advent of tandem mass spectrometry as a diagnostic tool allowed for the inclusion of many more conditions into screening programs, some of which do not fit the original criteria for inclusion. This presentation will discuss the current state of newborn screening for metabolic diseases and report on clinical outcome measures of patients identified by screening.     

Clinical suspicion of inborn errors of metabolism]

A number of inherited metabolic disorders are diagnosed by means of the nationwide newborn screening programme, usually before the first clinical signs occur. As for the rest of the varied metabolic disorders, knowledge and intuition of the paediatrician is a prerequisite for selection of patients for further metabolic investigation (selective screening procedure). Clinical symptoms of the most important metabolic diseases can be classified according to their pathophysiological background as: "intoxication type, energy deficiency type, storage type, neurodegenerative type". Especially in the first year of life, clinical features are unspecific: psychomotoric retardation, muscular hypotonia, cerebral convulsions, recurrent vomiting, sepsis-like conditions. In these cases indication for metabolic screening is broad. Especially in older children some clinical symptoms can be specific for a metabolic disorder: distinctive odour of urine, changes in hair, skin or eyes, organomegaly, skeletal changes. Recently, Reye-like syndrome, stridor, macrocephaly and vague, cerebral ischaemic episodes have been described in association with a metabolic defect. In conclusion, experience has shown that only a small number of metabolic disorders will be diagnosed from the typical clinical picture alone. In most cases a selective screening procedure leads to diagnosis because initial symptoms are unspecific.     

Primer on medical genomics. Part VIII: Essentials of medical genetics for the practicing physician

After the mapping and sequencing of the human genome, medical professionals from essentially all specialties turned their attention to investigating the role genes play in health and disease. Until recently, medical genetics was considered a specialty of minor practical relevance. This view has changed with the development of new diagnostic and therapeutic possibilities. It is now realized that genetic disease represents an important part of medical practice. Achievements in cancer genetics, in the field of prenatal diagnostics (including carrier testing for common recessive disorders), and in newborn screening for treatable metabolic disorders reinforce the rapidly expanding role of genetics in medicine. Diagnosing a genetic disorder not only allows for disease-specific management options but also has implications for the affected individual's entire family. A working understanding of the underlying concepts of genetic disease with regard to chromosome, single gene, mitochondrial, and multifactorial disorders is necessary for today's practicing physician. Routine clinical practice in virtually all medical specialties will soon require integration of these fundamental concepts for use in accurate diagnosis and ensuring appropriate referrals for patients with genetic disease and their families.     

Intelligent data analysis for the diagnosis of alcohol dependence syndrome

Alcohol dependence syndrome is hard to diagnose because none of the existing laboratory markers alone has sufficient specificity and sensitivity. This study investigated whether combinations of markers would improve the identification of patients with alcohol dependence syndrome. Intelligent data analysis was carried out using the decision tree induction method with training and test data from 244 healthy volunteers and 238 patients with alcohol dependence syndrome. The results showed that a combination of two or three laboratory markers can identify alcohol dependence syndrome with almost 85% accuracy. It must be noted that induced decision trees offer a qualitatively different diagnostic evaluation of laboratory findings that varies from common practice, because they set up their own new borders and criteria that are different to generally accepted or set reference values. Tests for all of the selected laboratory markers are widely available, inexpensive to perform and usually form part of a routine laboratory examination.     

Classification tree analysis for the discrimination of pleural exudates and transudates.

BACKGROUND: Classification and regression tree (CART) analysis is a non-parametric technique suitable for the generation of clinical decision rules. We have studied the performance of CART analysis in the separation of pleural exudates and transudates. METHODS: Basic demographic, radiologic and laboratory data were retrospectively evaluated in 1257 pleural effusions (204 transudates and 1053 exudates, according to standard clinical criteria) and submitted for CART analysis. The model's discriminative ability was compared with that of Light's criteria, in both the original formulation and an abbreviated version, i.e., deleting the pleural fluid (PF)/serum lactate dehydrogenase (LDH) ratio from the triad. RESULTS: A first CART model built starting from all available data identified PF/serum protein ratio and PF LDH ratios as the two best discriminatory parameters. This algorithm achieved a sensitivity of 96.8%, slightly lower than that of classical Light's criteria (98.5%) and comparable to that of the abbreviated Light's criteria (97.0%), and significantly better specificity (85.3%) compared to both classical (74.0%) and abbreviated (79.4%) Light's criteria. A second CART model developed after excluding serum measurements selected PF protein and PF LDH as the most discriminatory variables, and correctly classified 97.2% of exudates and 77.0% of transudates. CONCLUSIONS: CART-based algorithms can efficiently discriminate between pleural exudates and transudates.     

Acylcarnitine profiles during carnitine loading and fasting tests in a Japanese patient with medium-chain acyl-CoA dehydrogenase deficiency

Medium-chain acyl-CoA dehydrogenase deficiency (MCADD) is rare among Asian individuals, and the clinical course and biochemical findings remain unclear. We report herein a 3-year-old Japanese girl with MCADD. The diagnosis was suggested by acylcarnitine profiles and confirmed by enzyme activity and genetic analysis after clinical presentation. Our described method with high-performance liquid chromatography/tandem mass spectrometry allows quantification of levels of n-octanoylcarnitine (C8-N) and other isomers (e.g. valproylcarnitine). We examined the patient's acylcarnitine profiles in serum and urine samples during carnitine loading and 14-hr fasting tests with/without carnitine supplementation. Under hypocarnitinemia, serum level of C8-N was 0.16 micromol/l and C8-N/decanoylcarnitine (C10) ratio was 1.8, which did not correspond to the diagnostic criteria for MCADD. However, intravenous carnitine loading test (100 mg/kg/day for 3 days and 50 mg/kg/day for 1 day) led to increased serum C8-N levels and urinary excretion was obvious, strongly suggesting MCADD. In the fasting test with carnitine supplementation, marked production of acylcarnitines (C8-N > C2 > C6 > C10) was found, compared to the fasting test without carnitine supplementation. These results indicate that carnitine supplementation may be useful for detoxification of accumulated acylcarnitines even in an asymptomatic state. Moreover, the one-point examination for serum C8-N level and/or C8-N/C10 ratio may make the diagnosis of MCADD difficult, particularly in the presence of significant hypocarnitinemia. To avoid this pitfall, attention should be given to serum levels of free carnitine, and carnitine loading may be demanded in hypocarnitinemia.     

Electrospray tandem mass spectrometry for analysis of acylcarnitines in dried postmortem blood specimens collected at autopsy from infants with unexplained cause of death.

BACKGROUND: Deaths from inherited metabolic disorders may remain undiagnosed after postmortem examination and may be classified as sudden infant death syndrome. Tandem mass spectrometry (MS/MS) may reveal disorders of fatty acid oxidation in deaths of previously unknown cause. METHODS: We obtained filter-paper blood from 7058 infants from United States and Canadian Medical Examiners. Acylcarnitine and amino acid profiles were obtained by MS/MS. Specialized interpretation was used to evaluate profiles for disorders of fatty acid, organic acid, and amino acid metabolism. The analyses of postmortem blood specimens were compared with the analyses of bile specimens, newborn blood specimens, and specimens obtained from older infants at risk for metabolic disorders. RESULTS: Results on 66 specimens suggested diagnoses of metabolic disorders. The most frequently detected disorders were medium-chain and very-long-chain acyl-CoA dehydrogenase deficiencies (23 and 9 cases, respectively), glutaric acidemia type I and II deficiencies (3 and 8 cases, respectively), carnitine palmitoyl transferase type II/translocase deficiencies (6 cases), severe carnitine deficiency (4 cases), isovaleric acidemia/2-methylbutyryl-CoA dehydrogenase deficiencies (4 cases), and long-chain hydroxyacyl-CoA dehydrogenase/trifunctional protein deficiencies (4 cases). CONCLUSIONS: Postmortem metabolic screening can explain deaths in infants and children and provide estimates of the number of infant deaths attributable to inborn errors of metabolism. MS/MS is cost-effective for analysis of postmortem specimens and should be considered for routine use by Medical Examiners and pathologists in unexpected/unknown infant and child death.     

Applause sign: screening utility for dementia and cognitive impairment

Objective: To examine the diagnostic utility of applause sign scores for the diagnosis of dementia and mild cognitive impairment. Methods: Consecutive unselected new outpatient referrals to a dedicated cognitive disorders clinic over a 12-month period were administered the clapping test. Criterion diagnosis was by usual clinic assessment using standard diagnostic criteria, blind to applause sign score. Results: Applause sign scores differed significantly (p < 0.001) between diagnostic groups (dementia, mild cognitive impairment, subjective memory complaint) and did not correlate with other cognitive screening instrument scores. Nearly three-quarters of those with an abnormal score had cognitive impairment. Applause sign score was specific but not sensitive for a diagnosis of cognitive impairment. Conclusion: The applause sign supports a diagnosis of dementia or cognitive impairment in high prevalence settings and may be useful in conjunction with other cognitive screening tests.     

Digital microfluidics comes of age: high-throughput screening to bedside diagnostic testing for genetic disorders in newborns

Introduction: Digital microfluidics (DMF) is an emerging technology with the appropriate metrics for application to newborn and high-risk screening for inherited metabolic disease and other conditions that benefit from early treatment.

Areas covered: This review traces the development of electrowetting-based DMF technology toward the fulfillment of its promise to provide an inexpensive platform to conduct enzymatic assays and targeted biomarker assays at the bedside. The high-throughput DMF platform, referred to as SEEKER®, was recently authorized by the United States Food and Drug Administration to screen newborns for four lysosomal storage disorders (LSDs) and is deployed in newborn screening programs in the United States. The development of reagents and methods for LSD screening and results from screening centers are reviewed. Preliminary results from a more compact DMF device, to perform disease-specific test panels from small volumes of blood, are also reviewed. Literature for this review was sourced using principal author and subject searches in PubMed.

Expert commentary: Newborn screening is a vital and highly successful public health program. DMF technology adds value to the current testing platforms that will benefit apparently healthy newborns with underlying genetic disorders and infants at-risk for conditions that present with symptoms in the newborn period.