Newborn Screening Dried Blood Spots Research Articles

Improving sample rejection rate for newborn screening dried blood spot

Improving sample rejection rate for newborn screening dried blood spot

Newborn screening for lipid disorders.

Newborn screening is one of the most successful public health programs of the last century and offers unparalleled access to universal screening for a variety of metabolic and other disorders. Interest in development of newborn screening for lipid disorders has intensified in recent years. Screening newborns for lipid disorders has important implications for the health of the newborn as well as their relatives, and in the case of more common lipid disorders like familial hypercholesterolemia, could have important public health implications. Recent studies have demonstrated feasibility of measuring biomarkers for heterozygous familial hypercholesterolemia from newborn screening dried blood spot specimens. Another lipid disorder, cerebrotendinous xanthomatosis, is currently amenable to newborn screening utilizing currently available assays. New research in next-generation sequencing as a primary screen in newborns will also identify both common and rare lipid disorders in newborns. Historically, newborn screening for lipid disorders was not done for many reasons, but new research has developed testing methods that may successfully identify common and rare lipid disorders. This will impact the health of the newborn but could also impact family members and public health.

Stability of Amino Acids in Stored Dried Blood Spots: Retrospective Analysis

Residual newborn screening dried blood spots (DBS) are a valuable resource for research in the retrospective diagnosis of inborn errors of metabolism and biomarker analysis. Many metabolites are subject to degradation depending on time and storage conditions, such as temperature and humidity. We studied the stability of 15 amino acids (AAs) in dried blood spots stored in a refrigerator after newborn screening. Methods: We retrospectively analyzed the levels of 15 AAs in 248 residual DBS from the Kazakhstan neonatal screening program using tandem mass spectrometry. DBS were stored at 4°C and 55-70% humidity and randomly selected during 2019-2022. Amino acid stability was assessed using linear regression and estimating the decrease in concentration of each metabolite during each year. Results: Retrospective analysis of dried blood spot samples stored for one to four years showed that the decrease in concentrations of 15 AA occurred in order from most stable to least stable: valine, proline, isoleucine, leucine, tyrosine, phenylalanine, alanine, arginine, hydroxyproline, methionine, citrulline, glutamate, ornithine, glycine, and glutamine. Alanine, arginine, hydroxyproline, glycine, and glutamate decayed in line with linear regression. Conclusion: Storing dried blood spots at 4°C and 55-70% humidity is not optimal for amino acid stability. Data obtained from measuring amino acid levels in dried blood spots stored over time should be corrected to reduce the incidence of negative and false positive results.

Abstract 15499: Biochemical and Genetic Newborn Screening for Familial Hypercholesterolemia

Introduction: Familial Hypercholesterolemia (FH) causes elevated low-density lipoprotein cholesterol (LDL-C) and premature atherosclerosis. Despite guidelines, universal screening rates remain low. Newborn screening could increase FH diagnostic rates. Hypothesis: FH can be diagnosed from newborn dried blood spots for LDL-C, total cholesterol (TC), and apolipoprotein B (apoB), followed by selective genetic testing to identify pathogenic and likely pathogenic variants causing FH. Methods: De-identified, residual newborn screening dried blood spots were analyzed for LDL-C, TC, and apoB with results expressed as multiples of the median (MoM). Mahalanobis distance (measuring MoM different from 1) was computed and the top 8% of distances selected for genetic testing (panel including LDLR , APOB , PCSK9 , LDLRAP1 , APOE , LIPA , ABCG5 , and ABCG8 ). Results: A total of 10,004 specimens had biochemical testing, with 768 specimens selected for genetic testing. In total 15 variants were identified, 11 pathogenic and 4 likely pathogenic (Table 1). Composite Mahalanobis distance from LDL-C and apoB identified the most variants, followed by apoB alone and then LDL-C alone. TC alone identified the fewest number of variants (Table 2). Conclusions: Testing newborn dried blood spots with biochemical and reflex genetic testing is feasible to detect FH. Genetic testing of about 8% of samples identified 1 in 667 newborns with FH, but more extensive genetic testing would likely detect more variants. Prospective studies are needed to correlate newborn results with LDL-C levels later in childhood.

Biochemical and molecular characteristics among infants with abnormal newborn screen for very-long-chain acyl-CoA dehydrogenase deficiency: A single center experience

ObjectiveTo define the biochemical and molecular characteristics and diagnostic outcomes of a large US cohort of VLCAD deficiency positive cases as detected by newborn screening (NBS) with MS:MS. This relatively common disorder of fatty acid oxidation is screened for in every state in America and often results in extensive testing of multiple samples to arrive at a diagnostic conclusion. Materials and methodsWe compared NBS dried blood spot (DBS) acylcarnitine profile (ACP) C14, C14:1, C14:2, C14:1/C12:1 ratio and plasma C14, C14:1, C14:2, C14:1/C12:1, C14:1/C16 and C14:1/C2 ratios among true positive and false positive cases. Results of VLCAD enzyme analysis, molecular testing and fibroblast fatty acid oxidation probe assay were analyzed. ResultsThe presence of compound heterozygous or homozygous pathogenic variants, along with elevations of C14, C14:1 and C14:1/C12:1 ratio, identified 19 VLCAD deficiency cases. All were asymptomatic at most recent follow-up visits. The C14:1/C12:1 ratio in NBS-DBS ACP and plasma acylcarnitine profiles at follow-up (follow-up plasma ACP), is the most useful marker to differentiate between true and false positive cases. Among all cases with molecular analysis data available, approximately 56.7% had a single pathogenic mutation. Lymphocyte enzyme analysis (n = 61) was uninformative in 23% of cases studied. ConclusionVLCAD deficiency NBS by MS:MS is highly effective at identifying asymptomatic affected infants. Our cohort showed that elevation of C14:1/C12:1, in both NBS DBS and plasma ACP, was informative in discriminating affected from unaffected individuals and contributes to improve the accuracy of confirmatory testing of infants with presumptive positive for VLCAD deficiency.

Assessment of carnitine excretion and its ratio to plasma free carnitine as a biomarker for primary carnitine deficiency in newborns.

In the Netherlands, newborns are referred by the newborn screening (NBS) Program when a low free carnitine (C0) concentration (<5 μmol/l) is detected in their NBS dried blood spot. This leads to ~85% false positive referrals who all need an invasive, expensive and lengthy evaluation. We investigated whether a ratio of urine C0 / plasma C0 (RatioU:P) can improve the follow-up protocol for primary carnitine deficiency (PCD). A retrospective study was performed in all Dutch metabolic centres, using samples from newborns and mothers referred by NBS due to low C0 concentration. Samples were included when C0 excretion and plasma C0 concentration were sampled on the same day. RatioU:P was calculated as (urine C0 [μmol/mmol creatinine])/(plasma C0 [μmol/l]). Data were available for 59 patients with genetically confirmed PCD and 68 individuals without PCD. The RatioU:P in PCD patients was significantly higher (p value < 0.001) than in those without PCD, median [IQR], respectively: 3.4 [1.2-9.5], 0.4 [0.3-0.8], area under the curve (AUC) 0.837. Classified for age (up to 1month) and without carnitine suppletion (PCD; N= 12, Non-PCD; N= 40), medians were 6.20 [4.4-8.8] and 0.37 [0.24-0.56], respectively. The AUC for RatioU:P was 0.996 with a cut-off required for 100% sensitivity at 1.7 (yielding one false positive case). RatioU:P accurately discriminates between positive and false positive newborn referrals for PCD by NBS. RatioU:P is less effective as a discriminative tool for PCD in adults and for individuals that receive carnitine suppletion.

Nitrous oxide in labour predicted newborn screening total homocysteine and is a potential risk factor for infant vitamin B12 deficiency.

Risk factors for vitamin B12 deficiency in infants are not fully understood. The aim of the study was to assess predictors of total homocysteine and methylmalonic acid analysed in newborn screening dried blood spots. In a Norwegian case control study, we analysed total homocysteine and methylmalonic acid in newborn screening dried blood spots of 86 infants clinically diagnosed with vitamin B12 deficiency during 2012-2018. Results were compared to 252 healthy infants and 400 dried blood spot controls. Medical records were reviewed, and mothers completed questionnaires. Both total homocysteine and methylmalonic acid were significantly higher on newborn screening dried blood spots in infants later clinically diagnosed with vitamin B12 deficiency than controls. Multiple regression analysis showed that the dose of nitrous oxide during labour was the strongest predictor for total homocysteine level in newborn screening dried blood spots for all infants, with larger effect in infants later clinically diagnosed with vitamin B12 deficiency than controls. Nitrous oxide dose during labour was a predictor for total homocysteine and may impact the interpretation of total homocysteine analysis in newborn screening. Nitrous oxide is suggested as a contributing risk factor for infants prone to develop vitamin B12 deficiency.

Studying Autism Using Untargeted Metabolomics in Newborn Screening Samples

Main risk factors of autism spectrum disorder (ASD) include both genetic and non-genetic factors, especially prenatal and perinatal events. Newborn screening dried blood spot (DBS) samples have great potential for the study of early biochemical markers of disease. To study DBS strengths and limitations in the context of ASD research, we analyzed the metabolomic profiles of newborns later diagnosed with ASD. We performed LC-MS/MS-based untargeted metabolomics on DBS from 37 case-control pairs randomly selected from the iPSYCH sample. After preprocessing using MZmine 2.41, metabolites were putatively annotated using mzCloud, GNPS feature-based molecular networking, and MolNetEnhancer. A total of 4360 mass spectral features were detected, of which 150 (113 unique) could be putatively annotated at a high confidence level. Chemical structure information at a broad level could be retrieved for 1009 metabolites, covering 31 chemical classes. Although no clear distinction between cases and controls was revealed, our method covered many metabolites previously associated with ASD, suggesting that biochemical markers of ASD are present at birth and may be monitored during newborn screening. Additionally, we observed that gestational age, age at sampling, and month of birth influence the metabolomic profiles of newborn DBS, which informs us on the important confounders to address in future studies.

Newborn Screening Samples for Diabetes Research: An Underused Resource.

Inborn errors of metabolism and diabetes share common derangements in analytes of metabolic networks that are tested for in newborn screening, usually performed 48–72 h after birth. There is limited research examining the metabolic imprint of diabetes on newborn screening results. This paper aims to demonstrate the links between diabetes, biochemical genetics and newborn screening in investigating disease pathophysiology in diabetes, provide possible reasons for the lack of research in diabetes in newborn screening and offer recommendations on potential research areas. We performed a systematic search of the available literature from 1 April 1998 to 31 December 2018 involving newborn screening and diabetes using OVID, MEDLINE, Cochrane and the PROSPERO register, utilizing a modified extraction tool adapted from Cochrane. Eight studies were included after screening 1312 records. Five studies reanalyzed dried blood spots (DBS) on filter paper cards, and three studies utilized pre-existing results. The results of these studies and how they relate to cord blood studies, the use of cord blood versus newborn screening dried blood spots as a sample and considerations on newborn screening and diabetes research is further discussed. The timing of sampling of newborn screening allows insight into neonatal physiology in a catabolic state with minimal maternal and placental influence. This, combined with the wide coverage of newborn screening worldwide, may aid in our understanding of the origins of diabetes.

Neonatal carnitine concentrations in relation to gestational age and weight.

BackgroundFree carnitine has been measured in the Dutch newborn screening (NBS) program since 2007 with a referral threshold of ≤5 μmol/L, regardless of gestational age or birthweight. However, several studies suggest that carnitine concentrations may depend on gestational age and birthweight. We evaluated differences in postnatal day‐to‐day carnitine concentrations in newborns based on gestational age (GA) and/or weight for GA (WfGA).MethodsA retrospective study was performed using data from the Dutch NBS. Dried blood spot (DBS) carnitine concentrations, collected between the 3rd and 10th day of life, of nearly 2 million newborns were included. Individuals were grouped based on GA and WfGA. Median carnitine concentrations were calculated for each group. Mann‐Whitney U tests, and chi‐square tests were applied to test for significant differences between groups.ResultsPreterm, postterm, and small for GA (SGA) newborns have higher carnitine concentrations at the third day of life compared to term newborns. The median carnitine concentration of preterm newborns declines from day 3 onwards, and approximates that of term newborns at the sixth day of life, while median concentrations of postterm and SGA newborns remain elevated at least throughout the first 10 days of life. Carnitine concentrations ≤5 μmol/L were found less frequently in SGA newborns and newborns born between 32 and 37 weeks of gestation, compared to term newborns.ConclusionsMedian carnitine concentrations in NBS DBS vary with day of sampling, GA, and WfGA. It is important to take these variables into account when interpreting NBS results..

Second Tier Molecular Genetic Testing in Newborn Screening for Pompe Disease: Landscape and Challenges.

Pompe disease (PD) is screened by a two tier newborn screening (NBS) algorithm, the first tier of which is an enzymatic assay performed on newborn dried blood spots (DBS). As first tier enzymatic screening tests have false positive results, an immediate second tier test on the same sample is critical in resolving newborn health status. Two methodologies have been proposed for second tier testing: (a) measurement of enzymatic activities such as of Creatine/Creatinine over alpha-glucosidase ratio, and (b) DNA sequencing (a molecular genetics approach), such as targeted next generation sequencing. (tNGS). In this review, we discuss the tNGS approach, as well as the challenges in providing second tier screening and follow-up care. While tNGS can predict genotype-phenotype effects when known, these advantages may be diminished when the variants are novel, of unknown significance or not discoverable by current test methodologies. Due to the fact that criticisms of screening algorithms that utilize tNGS are based on perceived complexities, including variant detection and interpretation, we clarify the actual limitations and present the rationale that supports optimizing a molecular genetic testing approach with tNGS. Second tier tNGS can benefit clinical decision-making through the use of the initial NBS DBS punch and rapid turn-around time methodology for tNGS, that includes copy number variant analysis, variant effect prediction, and variant ‘cut-off’ tools for the reduction of false positive results. The availability of DNA sequence data will contribute to the improved understanding of genotype-phenotype associations and application of treatment. The ultimate goal of second tier testing should enable the earliest possible diagnosis for the earliest initiation of the most effective clinical interventions in infants with PD.

Neonatal Macrosomia is an Interfering Factor for Analytes on the Colorado State Newborn Screen.

Neonatal macrosomia is a known complication of maternal obesity and gestational diabetes, and it is a risk factor for obesity and diabetes in offspring. Amino acids and acylcarnitines are biomarkers for obesity in children and adults. These analytes, which are also routinely obtained on the newborn screen, have not been well-characterized in macrosomic newborns. The impact of macrosomia on rates of false-positive results in the newborn screen has also not been well-studied. We test the hypothesis that macrosomia is an interfering factor for amino acids and/or acylcarnitines on the newborn screen. Newborn screening analytes determined by tandem mass spectroscopy were obtained from the Colorado Department of Public Health and Environment archives (2016-2018). This included metabolite concentrations obtained at 24-72 hours of life from newborns with birth weight 2500 to 3999 g (nonmacrosomic, n = 131 896) versus 4000 to 8000 g (macrosomic, n = 7806). Mother/infant phenotypic data were limited to information provided on the newborn screening dried blood spot card. Data were analyzed using Student t-test and chi-squared analysis. Macrosomic newborns had elevations in C2, C3, dicarboxylic, and long-chain acylcarnitines (specifically C16 and C18 species). C3 and C18:1 were 2 to 3 times more likely to be above predetermined state cutoffs in macrosomic versus nonmacrosomic newborns (both male and female). Macrosomia is an interfering factor for the analytes C3 and C18:1, leading to higher risk of false-positive results for methylmalonic/propionic acidemia and carnitine palmitoyl transferase type 2 deficiency, respectively. Analyte patterns found in macrosomic neonates correspond with similar analyte patterns in obese children and adults.

Metabolic profiles derived from residual blood spot samples: A longitudinal analysis

Background: Secondary use of newborn screening dried blood spot samples include use for biomedical or epidemiological research. However, the effects of storage conditions on archival samples requires further examination. The objective of this study was to determine the utility of residual newborn samples for deriving reliable metabolic gestational age estimates. Methods: Residual newborn dried blood spot samples that had been stored for 2-, 4-, 6-, or 12-months in temperature controlled (21°C) conditions were re-analyzed for the full panel of newborn screening analytes offered by a provincial newborn screening lab in Ottawa, Canada. Data from re-analyzed samples were compared to corresponding baseline newborn screening values for absolute agreement, and Pearson and intraclass correlation. Performance of a gestational age estimation algorithm originally developed from baseline newborn screening values was then validated on data derived from stored samples. Results: A total of 307 samples were used for this study. 17-hydroxyprogesterone and newborn hemoglobin profiles measured by immunoassay and high-performance liquid chromatography, respectively, were among the most stable markers across all time points of analysis. Acylcarnitines exhibited the greatest degree of variation in stability upon repeat measurement. The largest shifts in newborn analyte profiles and the poorest performance of metabolic gestational age algorithms were observed when samples were analyzed 12-months after sample collection. Conclusions: Duration of sample storage, independent of temperature and humidity, affects newborn screening profiles and gestational age estimates derived from metabolic gestational dating algorithms. When considering use of dried blood spot samples either for clinical or research purposes, care should be taken when interpreting data stemming from secondary use.

Metabolic profiles derived from residual blood spot samples: A longitudinal analysis.

Background: Secondary use of newborn screening dried blood spot samples include use for biomedical or epidemiological research. However, the effects of storage conditions on archival samples requires further examination. The objective of this study was to determine the utility of residual newborn samples for deriving reliable metabolic gestational age estimates. Methods: Residual newborn dried blood spot samples that had been stored for 2-, 4-, 6-, or 12-months in temperature controlled (21°C) conditions were re-analyzed for the full panel of newborn screening analytes offered by a provincial newborn screening lab in Ottawa, Canada. Data from re-analyzed samples were compared to corresponding baseline newborn screening values for absolute agreement, and Pearson and intraclass correlation. Performance of a gestational age estimation algorithm originally developed from baseline newborn screening values was then validated on data derived from stored samples. Results: A total of 307 samples were used for this study. 17-hydroxyprogesterone and newborn hemoglobin profiles measured by immunoassay and high-performance liquid chromatography, respectively, were among the most stable markers across all time points of analysis. Acylcarnitines exhibited the greatest degree of variation in stability upon repeat measurement. The largest shifts in newborn analyte profiles and the poorest performance of metabolic gestational age algorithms were observed when samples were analyzed 12-months after sample collection. Conclusions: Duration of sample storage, independent of temperature and humidity, affects newborn screening profiles and gestational age estimates derived from metabolic gestational dating algorithms. When considering use of dried blood spot samples either for clinical or research purposes, care should be taken when interpreting data stemming from secondary use.

The Influence of Education on Public Trust and Consent Preferences With Residual Newborn Screening Dried Blood spots.

The objectives of this study were to evaluate the impact of educational interventions during prenatal care on public trust for newborn screening and consent preferences for the retention and use of leftover newborn screening dried blood spots. Women who were 30 to 36 weeks pregnant were recruited, and outcomes were measured by telephone survey 2 to 4 weeks postpartum (n = 901). Approximately 40% of the sample chose the opt-out approach but those who watched educational interventions delivered during prenatal care were significantly associated with higher levels of trust and support for an opt-out consent approach. Providing education during prenatal care about newborn screening and the storage and use of leftover dried blood spots along with brochure-based education provided in the hospital when the baby is born is associated with improved trust for the program and support for research with the leftover blood spots.

Development of filter paper hemoglobin A1c assay applicable to newborn screening

PurposeGestational diabetes influences risk for future metabolic disease including type 2 diabetes. Hemoglobin A1c (HbA1c) measurement assesses hemoglobin A glycosylation, and could theoretically be used as a test to estimate gestational glucose exposure. HbA1c assay on dried blood spots (DBS) is needed before potential application to statewide newborn screening (NBS) population studies. The study aimed to establish a reliable method to measure HbA1c on NBS DBS specimens. De-identified blood was used to generate trials to evaluate stability of HbA1c in DBS, optimal elution time, and stability of eluted blood. ResultsAnalysis of DBS stability HbA1c measurements from 3 to 6days after collection overestimated HbA1c values by a bias factor between 0.83 and 0.87. Sixty minutes of elution time produced maximal reproducibility and minimal bias of results. Within assay standard deviation: 0.058; average bias: −0.02%. Stability of eluted blood did not vary significantly between days 0–2 after DBS elution. ConclusionsMeasurement of HbA1c levels on DBS from human blood is feasible. Results suggest new method using DBS to measure HbA1c level with the following characteristics: optimal time for sample analysis 3–6days after collection, elution time of 60min and eluted blood analysis within 2days of elution. Measurement of neonatal HbA1c could provide insight regarding the infant's in utero exposure to glucose.

Screening and prevention of neonatal glucose 6-phosphate dehydrogenase deficiency in Guangzhou, China.

We aimed to summarize the results of screening protocol and prevention of neonatal glucose 6-phosphate dehydrogenase (G6PD) deficiency during a 22-year-long period to provide a basis of reference for the screening of this disease. About 1,705,569 newborn subjects in Guangzhou City were screened for this deficiency. Specimens were collected according to the conventional method of specimen acquisition for "newborn dried bloodspot screening", preserved, and inspected. The specimens were studied with fluorescent spot test and quantitative fluorescence assay. Diagnosis was performed using the modified NBTG6PD/6PGD ratio method. Bloodspot filter paper specimens were sent to the laboratory within 24 h via EMS Express, and the G6PD test was performed on the same day. The G6PD deficiency-positive rate was 4.2% in the samples screened using the fluorescent spot test, while it was 5% in case of the quantitative fluorescence assay. Neonatal screening for G6PD deficiency for 11,437 cases (6117 boys and 5320 girls) showed positive results in 481 cases. About 420 cases (318 boys and 102 girls) of G6PD deficiency were confirmed with the modified Duchenne NBT ratio method. The total detection rate was 3.7:5.2% for boys and 1.9% for girls. Quantitative fluorescence assay improved the sensitivity and detection rate. Accelerating the speed of sample delivery by using Internet network systems and ensuring online availability of screening results can aid the screening and diagnosis of this deficiency within 1 week of birth.

Accuracy of prenatal smoking data from Washington State birth certificates in a population-based sample with cotinine measurements

PurposeTo assess the accuracy of smoking data in contemporary U.S. birth certificates. MethodsWe compared data on prenatal smoking as reported on Washington State birth certificates to cotinine measured in archived newborn screening dried blood spots for 200 infants born in 2007 (100 randomly selected from births to self-reported nonsmokers and 100 born to self-reported smokers). We estimated the sensitivity of the birth certificate data to identify prenatal smokers and the precision with which self-identified third trimester smokers report smoking levels. ResultsInfants born to two (2%) mothers who reported they did not smoke during the pregnancy had whole blood cotinine concentrations consistent with active smoking by the mother (sensitivity 85%). Sensitivity of the birth certificate to identify reported smokers who continued to smoke throughout pregnancy was similar (89%). Among self-identified third trimester smokers whose infants' specimens were collected shortly after delivery, Spearman rho between infant cotinine and maternal-reported cigarettes/day in the third trimester was 0.54. ConclusionsBirth certificates may represent a viable option for assessing prenatal smoking status, and possibly smoking cessation and level among smokers, in epidemiologic studies sufficiently powered to overcome a moderate amount of exposure measurement error.

A comparative study on detection of amino acids in newborns using two assay methods with tandem mass spectrometry

Objective To provide methodological references for laboratories to carry out newborn screening for disorders of amino acid metabolism,we compared the difference and distribution of ten amino acids including alanine (Ala),arginine (Arg),citrulline (Cit),glycine (Gly),leucine (Leu),methionine (Met),ornithine (Orn),phenylalanine (Phe),tyrosine (Tyr),and valine (Val) from newborn dried blood spots specimen using derivatization or non-derivatization as sample preparation methods. Method It is a comparative research study.A total of 4135 newborn screening dried blood spot samples for inborn errors of metabolism were collected from January to June,2012.All specimens came from neonatal screening center of shanghai children′s hospital.Samples were prepared by two different techniques,the corresponding kits and the procedures were used as follows: (1) Simultaneous detection of 100 dried blood spot specimens using two methods respectively to compare the paired difference of each amino acid. (2) 2000 cases of normal newborn specimens were detected respectively to obtain the normal distribution of ten neonatal amino acids. (3) 35 specimens from patients previously diagnosed positively as inborn errors of metabolism were simultaneously detected with 7 amino acids to verify the consistency of two techniques in clinical judgment. Results The amino acid levels of normal newborns analyzed by one-sample kolmogorov-Smirnov test (Z value ranged from 1.997 to 6.229) showed a skewed distribution (P 0.05).According to 0.5th to 99.5th percentiles,the normal reference range for derivatization method were greater than onderivatization method,and the average value was 25.3%.After clinic judgment,the results of the abnormal indicators of children with true metabolism disorders showed no statistically significant between two methods (P>0.05),the detection rate was 100%. Conclusions There was a slight difference between derivatization and the non-derivatization techniques in detecting multiple amino acids.The results of the abnormal indicators of amino acid metabolism disorders show no statically significant difference between the two methods,and no difference in clinical judgment.Both methods can be used in detecting amino acid metabolism disorders in newborn screening.(Chin J Lab Med,2013,36:908-911) Key words: Amino acids; Tandem mass spectrometry; Specimen handling; Comparative study

Metabonomics of Newborn Screening Dried Blood Spot Samples: A Novel Approach in the Screening and Diagnostics of Inborn Errors of Metabolism

A novel, single stage high resolution mass spectrometry-based method is presented for the population level screening of inborn errors of metabolism. The approach proposed here extends traditional electrospray tandem mass spectrometry screening by introducing nanospray ionization and high resolution mass spectrometry, allowing the selective detection of more than 400 individual metabolic constituents of blood including acylcarnitines, amino acids, organic acids, fatty acids, carbohydrates, bile acids, and complex lipids. Dried blood spots were extracted using a methanolic solution of isotope labeled internal standards, and filtered extracts were electrosprayed using a fully automated chip-based nanospray ion source in both positive and negative ion mode. Ions were analyzed using an Orbitrap Fourier transformation mass spectrometer at nominal mass resolution of 100,000. Individual metabolic constituents were quantified using standard isotope dilution methods. Concentration threshold (cutoff) level-based analysis allows the identification of newborns with metabolic diseases, similarly to the traditional electrospray tandem mass spectrometry (ESI-MS/MS) method; however, the detection of additional known biomarkers (e.g., organic acids) results in improved sensitivity and selectivity. The broad range of detected analytes allowed the untargeted multivariate statistical analysis of spectra and identification of additional diseased states, therapeutic artifacts, and damaged samples, besides the metabolic disease panel.