Biomedical subjects

Edwin W Naylor

Publications and source records attributed to Edwin W Naylor.

9 recordsLinked to original sources

PubMed2005

Alternative DNA-based newborn screening for glucose-6-phosphate dehydrogenase deficiency.

Newborn screening for G6PD deficiency has been carried out in several countries for more than 25 years. A semi-quantitative enzymatic assay has been used in most laboratories, however, heat inactivation during the summer can cause a significant increase in the false positive rate for this assay. We have developed an alternative DNA-based newborn screening assay for the detection of common mutations within the G6PD gene. The panel of mutations includes the common African A- mutation (G202A;A376G), the common Mediterranean mutation (C563T), and two common Chinese mutations (G1376T and G1388A). A parallel study was performed through screening a total of 4245 neonatal specimens using both the enzymatic and the DNA-based assays. In this population, 49 newborns were identified as hemizygous or homozygous for the A- mutation with an average enzyme activity of 59 microM, 323 were identified as a carrier or unaffected with an average enzyme activity of 208 microM, and no mutation was detected for the remaining 3873 specimens with an average enzyme activity of 234 microM. With this panel of mutations, more than 90% of all affected infants can be identified in our population.

Base Sequence↗

PubMed2004

The use of filter paper-dried blood spots for thyroid-antibody screening in adults.

Thyroid-antibody screening is recommended for several adult populations, including the elderly and pregnant and postpartum women, and analysis of filter paper-dried blood spots (DBSs) has been a cost-effective means of screening newborns for hypothyroidism for more than 30 years. The aim of this study was to show that DBS specimens can be used to test adults for thyroid-stimulating hormone (TSH) antibodies and thyroid antibodies during screening for thyroid disease in a community setting. Thyroid peroxidase antibody and thyroglobilin antibody enzyme-linked immunosorbent assay kits for serum have been adapted for use with DBSs. A TSH assay for newborn DBSs was adapted for the screening of adults. Parallel specimens, serum and DBSs, were collected during routine care of patients attending a thyroid clinic. In addition, 962 DBS specimens were collected from volunteers at community centers and nursing homes. Twelve months later, a second specimen was collected from each of 411 original volunteers. Antibody results are reported as normal and positive. Ninety-seven percent of the serum/DBS results correlated exactly. Of 962 volunteers from nursing homes and community centers, testing for antibodies was positive or indeterminate (borderline) in 266 (27%). Eighty percent of the patients with an initially normal TSH reading who were positive on the 12-month collection were positive for at least one antibody in the first collection. The use of DBSs is a convenient and efficient way to screen for thyroid antibody as a means of detecting occult thyroid disease in adults.

Adult↗

PubMed2004

A high throughput beta-globin genotyping method by multiplexed melting temperature analysis.

For a population-based newborn screening program, challenges exist in using technological advances to improve the quality and efficiency of the existing screening program and to develop new diagnostic capabilities. A newly developed genotyping method for screening of common mutations within the beta-globin gene is described here. This genotyping system consists of three major components: an automation system for high throughput DNA extraction and PCR setup, a conventional thermal cycler, and a LightTyper instrument for post-PCR melting temperature analysis. Briefly, genomic DNA is extracted from dried blood on a filter paper using methanol and Tris buffer. Genetic fragments of interest are amplified by asymmetric PCR. Fluorescent labeled probes are added during PCR setup, which eliminates the need for any post-PCR sample handling process. Melting temperature analysis is achieved through fluorescent resonance energy transfer (FRET) reaction using the LightTyper instrument. The assay is designed to simultaneously detect three common beta-globin mutations, S(A173T), C(G172A), and E(G232A), and can identify any of the eight possible genotypes in a single reaction: AA, AE, EE, AS, SC, SS, AC, and CC (A represents wild type allele). The method was validated with a large number of samples in both a retrospective and parallel study. Results were compared to those obtained by isoelectric focusing electrophoresis. The accuracy of this genotyping method is greater than 99%.

DNA↗

PubMed2003

Effect of expanded newborn screening for biochemical genetic disorders on child outcomes and parental stress.

CONTEXT: Tandem mass spectrometry now allows newborn screening for more than 20 biochemical genetic disorders. Questions about the effectiveness and risks of expanded newborn screening for biochemical genetic disorders need to be answered prior to its widespread acceptance as a state-mandated program. OBJECTIVES: To compare newborn identification by expanded screening with clinical identification of biochemical genetic disorders and to assess the impact on families of a false-positive screening result compared with a normal result in the expanded newborn screening program. DESIGN: Prospective study involving an inception cohort of newly diagnosed children. SETTING: Massachusetts, Maine, and a private laboratory in Pennsylvania with expanded newborn screening; other New England states with limited screening. PARTICIPANTS: Families of 50 affected children identified through expanded newborn screening (82% of eligible cases); 33 affected children identified clinically (97% of eligible cases); 94 screened children with false-positive results (75% of eligible cases); and 81 screened children with normal results (63% of eligible cases). MAIN OUTCOME MEASURES: Child's health and development and the Parental Stress Index. RESULTS: Within the first 6 months of life, 28% of children identified by newborn screening compared with 55% of clinically identified children required hospitalization (P =.02). One child identified by newborn screening compared with 8 (42%) identified clinically performed in the range of mental retardation (P<.001). Mothers in the screened group reported lower overall stress on the Parental Stress Index than mothers in the clinically identified group (z = 3.38, P<.001). Children with false-positive results compared with children with normal results were twice as likely to experience hospitalization (21% [n = 20] vs 10% [n = 8], respectively; P =.06). Mothers of children in the false-positive group compared with mothers of children with normal screening results attained higher scores on the Parental Stress Index (z = 4.25, P<.001) and the Parent-Child Dysfunction subscale (z = 5.30, P<.001). CONCLUSIONS: Expanded newborn screening may lead to improved health outcomes for affected children and lower stress for their parents. However, false-positive screening results may place families at risk for increased stress and parent-child dysfunction.

Adult↗

PubMed2003

Neonatal blood carnitine concentrations: normative data by electrospray tandem mass spectometry.

Despite a number of published reports, there is limited information about carnitine metabolism in the newborn. To establish normative data, we analyzed whole-blood carnitine concentrations in 24,644 newborns at age 1.85 +/- 0.95 d and umbilical cord whole blood and plasma carnitine concentrations in 50 full-term newborns. Total carnitine (TC), free carnitine (FC), and acylcarnitine (AC) were measured by electrospray tandem mass spectrometry. AC/FC ratios were derived from these measurements. The entire cohort was stratified according to TC values into a middle TC group representing 90% of the population and lower and upper TC groups representing 5% of the population, respectively. Normative data were derived from the middle TC group of full-term infants (N = 19,595). TC was 72.42 +/- 20.75 microM, FC was 44.94 +/- 14.99 microM, AC was 27.48 +/- 8.05 microM, and AC/FC ratio was 0.64 +/- 0.19 (+/-SD). These values differed significantly from umbilical cord whole blood TC values of 31.27 +/- 10.54 microM determined in 50 samples. No meaningful correlation was found between TC and gestational age or birth weight in any group. In controlled analyses, prematurity was not associated with TC levels, whereas low birth weight (<2500 g) and male sex were significantly associated with higher TC levels. The association of low birth weight with higher TC values may be related to decreased tissue carnitine uptake. The sex effect may be related to hormonal influences on carnitine metabolism. Our study provides normative data of carnitine values measured by the highly precise method of electrospray tandem mass spectrometry in a large cohort of newborns and provides the basis for future studies of carnitine metabolism in health and disease states during the neonatal period.

Carnitine↗

PubMed2003

Real time PCR assays to detect common mutations in the biotinidase gene and application of mutational analysis to newborn screening for biotinidase deficiency.

Biotinidase deficiency is an autosomal recessive disorder of biotin metabolism caused by defects in the biotinidase gene. Symptoms of biotinidase deficiency are resolved or prevented with oral biotin supplementation and as such newborn screening is performed to prospectively identify affected individuals prior to the onset of symptoms. Biotinidase deficiency is detected by determining the activity of the biotinidase enzyme utilizing the newborn dried blood spot and colorimetric end point analysis. While newborn screening by enzyme analysis is effective, external factors may compromise results of the enzyme analysis and difficulty is encountered in distinguishing between complete and partial enzyme deficiencies. In the United States, the four mutations most commonly associated with complete biotinidase deficiency are c98:d7i3, Q456H, R538C, and the double mutation D444H:A171T. Partial biotinidase deficiency is almost universally attributed to the D444H mutation. To more effectively distinguish between profound and partial biotinidase deficiency, a panel of assays utilizing real time PCR and melting curve analysis using Light Cycler technology was developed. Employing DNA extracted from the original dried blood specimens from newborns identified through prospective newborn screening as presumptive positive for biotinidase deficiency, the specimens were analyzed for the presence of the five common mutations. Using this approach it was possible to separate newborns with partial and complete deficiency from each other as well as from many of those with false positive results. In most cases it was also possible to correlate the genotype with the degree of residual enzyme activity present. In newborn screening for biotinidase deficiency, we have shown that the analysis of common mutations is useful in distinguishing between partial and complete enzyme deficiency as well as improving specificity. Combining biotinidase enzyme analysis with genotypic data also increases the sensitivity of screening for biotinidase deficiency and provides information useful to clinicians earlier than would otherwise be possible.

Amidohydrolases↗

PubMed2003

Analysis of common mutations in the galactose-1-phosphate uridyl transferase gene: new assays to increase the sensitivity and specificity of newborn screening for galactosemia.

Classical galactosemia is a genetic disease caused by mutations in the galactose-1-phosphate uridyl transferase (GALT) gene. Prospective newborn screening for galactosemia is routine and utilizes the universally collected newborn dried blood specimen on filter paper. Screening for galactosemia is achieved through analysis of total galactose (galactose and galactose-1-phosphate) and/or determining the activity of the GALT enzyme. While this approach is effective, environmental factors and the high frequency of the Duarte D2 mutation (N314D) does lead to false positive results. Using DNA derived from the original newborn dried blood specimen and Light Cycler technology a panel of five assays able to detect the four most frequently encountered classical galactosemia alleles (Q188R, S135L, K285N, and L195P) and the N314D Duarte variant mutation are described. The five assays are performed simultaneously using common conditions. Including DNA preparation, set-up, amplification, and analysis the genotype data for all five loci is obtained in less than 2 hours. The assays are easily interpreted and amenable to high-throughput newborn screening. Mutational analysis is useful to reduce false positive results, differentiate D/G mixed heterozygotes from classical galactosemia, and to clearly identify a very high percentage of those affected by classical galactosemia.

Base Sequence↗

PubMed2003

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.

Amino Acid Metabolism, Inborn Errors↗

PubMed2002

The application of tandem mass spectrometry to neonatal screening for inherited disorders of intermediary metabolism.

This review is intended to serve as a practical guide for geneticists to current applications of tandem mass spectrometry to newborn screening. By making dried-blood spot analysis more sensitive, specific, reliable, and inclusive, tandem mass spectrometry has improved the newborn detection of inborn errors of metabolism. Its innate ability to detect and quantify multiple analytes from one prepared blood specimen in a single analysis permits broad recognition of amino acid, fatty acid, and organic acid disorders. An increasing number of newborn screening programs are either utilizing or conducting pilot studies with tandem mass spectrometry. It is therefore imperative that the genetics community be familiar with tandem mass spectrometric newborn screening.

Amino Acid Metabolism, Inborn Errors↗