Maternal screening for hypothyroidism and thyroiditis using filter paper specimens

BACKGROUND AND OBJECTIVE

Hypothyroidism and autoimmune thyroiditis are more prevalent than previously considered in women during pregnancy and the postpartum, and are associated with adverse effects on the mother and her fetus. We determined the efficacy and accuracy of screening women for primary hypothyroidism and autoimmune thyroiditis by testing TSH and two thyroid antibodies (TAb): thyroperoxidase antibodies (TPOAb) and thyroglobulin antibodies (TgAb), in eluates of filter paper specimens collected during early pregnancy and the postpartum.

METHODS

We enrolled 494 first-trimester pregnant women with no exclusion criteria into a prospective study to detect primary hypothyroidism and autoimmune thyroiditis. Finger stick blood was applied to filter paper, dried in room air, eluted, and promptly tested for TSH and TAb. A total of 178 of the pregnant women (36%) were tested in the early postpartum. Women with abnormal results had confirmatory serum tests.

RESULTS

It was found that 91 pregnant women (18.4%) and 43 postpartum women (24.2%) had abnormal TSH values (>4.0 mU/L) and/or positive TAb; 140 pregnant women (28.3%) had TSH values >2.5 mU/L. All subjects with TSH values >4.0 mU/L tested positive for TAb. Eighteen women (3.6%) who tested normal during pregnancy tested abnormal in the postpartum.

CONCLUSIONS

This study confirms that TSH and TPOAb measured in eluates of blood-spotted filter paper specimens are excellent screening tests to detect primary hypothyroidism and autoimmune thyroiditis in pregnant and postpartum women. Results are very comparable to serum data in this population published in the literature.

A limited spectrum of phenylalanine hydroxylase mutations is observed in phenylketonuria patients in western Poland and implications for treatment with 6R tetrahydrobiopterin

Phenylketonuria (PKU) is an autosomal recessive defect in hepatic metabolism of phenylalanine, which is secondary to mutations in the phenylalanine hydroxylase (PAH) gene. Sixty-seven ethnically Polish PKU patients, followed at the Outpatient Department of Pediatrics and Developmental Medicine in Poznan, Poland, were assessed for mutations in the PAH gene. Two mutations were identified in 61 of 67 patients and a single mutation was identified in the remaining six patients. The four most prevalent mutations (p.R408W, 68%; c.1066-11G>A, 6%; c.1315+1G>A, 5.2%; c.822-832delGCCCATGTATA, 3.7%) accounted for 83% of the mutant alleles. Fifteen additional mutations were identified of which most (13/15) were observed in an individual patient. Before knowledge of PAH genotypes, 19 patients were challenged with a 20 mg kg(-1) dose of 6R tetrahydrobiopterin (BH(4)) and serum phenylalanine concentration was monitored in hospital over 24 h. Two patients responded to the BH(4) challenge with a reduction of serum phenylalanine concentration >30% from baseline. PAH genotypes of the two responsive patients would have been predicted, as they contained mutations recognized as BH(4) responsive, whereas the 17 patients who were unresponsive would have been predicted as their mutations were either recognized as non-responsive or were highly deleterious frame-shift mutations. Overall, only 7.5% (5/ 67) of patients had PAH mutations recognized as responsive to co-factor therapy. Among the PKU patients from western Poland, PAH mutations responsive to BH(4) therapy are poorly represented; therefore, genotyping may be useful for identifying candidate patients likely to respond to BH(4) before physiological challenge.

Biochemical characterization of mutant phenylalanine hydroxylase enzymes and correlation with clinical presentation in hyperphenylalaninaemic patients

The biochemical properties of mutant phenylalanine hydroxylase (PAH) enzymes and clinical characteristics of hyperphenylalaninaemic patients who bear these mutant enzymes were investigated. Biochemical characterization of mutant PAH enzymes p.D143G, p.R155H, p.L348V, p.R408W and p.P416Q included determination of specific activity, substrate activation, V(max), K(m) for (6R)-L-erythro-5,6,7,8-tetrahydrobiopterin (BH(4)), K (d) for BH(4), and protein stabilization by BH(4). Clinical data from 22 patients either homozygous, functionally hemizygous, or compound heterozygous for the mutant enzymes of interest were correlated with biochemical parameters of the mutant enzymes. The p.L348V and p.P416Q enzymes retain significant catalytic activity yet were observed in classic and moderate PKU patients. Biochemical studies demonstrated that BH(4) rectified the stability defects in p.L348V and p.P416Q; additionally, patients with these variants responded to BH(4) therapy. The p.R155H mutant displayed low PAH activity and decreased apparent affinity for L-Phe yet was observed in mild hyperphenylalaninaemia. The p.R155H mutant does not display kinetic instability, as it is stabilized by BH(4) similarly to wild-type PAH; thus the residual activity is available under physiological conditions. The p.R408W enzyme is dysfunctional in nearly all biochemical parameters, as evidenced by disease severity in homozygous and hemizygous patients. Biochemical assessment of mutant PAH proteins, especially parameters involving interaction with BH(4) that impact protein folding, appear useful in clinical correlation. As additional patients and mutant proteins are assessed, the utility of this approach will become apparent.

Assays for thyroid-stimulating hormone using dried blood spotted filter paper specimens to screen for hypothyroidism in older children and adults

OBJECTIVE

Symptoms of hypothyroidism in adults can be mistaken for medical and psychiatric diseases, as well as for general signs of ageing such as weakness, lethargy and fatigue. The incidence of hypothyroidism is many-fold higher in adults than in newborn children. The latter have been routinely screened for the condition using filter paper dried blood spots (DBS) for nearly three decades but this cost-effective screening technique has only recently been applied to adults. This study was undertaken to show that DBS testing in adults and older children is an accurate way to screen for hypothyroidism.

METHODS

Serum and DBS specimens were collected from adults and children. Assays were run on both specimens and the results correlated. In addition 972 specimens were collected from adults at community centres and nursing homes. Follow-up studies were performed on patients with positive results.

RESULTS

The correlation coefficient for 118 matched serum and DBS specimens was 0.99. Thyroid-stimulating hormone (TSH) values were elevated in 50 of the 972 adults from nursing homes and community centres. Thirteen of these individuals were on thyroid medication and 28 had either high serum TSH or high thyroglobulin (TgAb) or thyroid peroxidase (TPOAb) antibody levels.

CONCLUSIONS

Individuals can be screened for hypothyroidism by collecting finger stick DBS specimens at community centres, nursing homes and other locations which can be mailed by regular postal service to a central laboratory for accurate and inexpensive testing.

Inherited metabolic disorders in Thailand--Siriraj experience

The incidence of inborn errors of metabolism (IEM) in Thailand is yet unknown. However, by estimation it is generally accepted to be 1 in 5,000. From a survey in 7 medical schools from different parts of the country and a large pediatric hospital in Bangkok, we found numerous cases of IEM nationwidc. Thesc were amino acid disorders, carbohydrate disorders, urea cycle defects, peroxisomal, lysosomal storage disorders, and many others. Since Thais are quite homogeneous in their genetic make-up; it is, therefore, very likely that IEM is much more prevalent than we realized. With the exception of thalassemias, IFAM is probably very common in Thailand and other countries in the Asia-Pacific region. IEM identified were amino acid disorders eg phenylketonuria, maple syrup urine disease: urea cycle disorders eg ornithine transcarbamylase deficincy (OTC), argininosuccinic lyase deficiency (ALD), argininosuccinic acid synthetasc deficiency (ASD); glycogen storage disorders eg Pompe's discase, Von Gierkc's; organic acid disorders eg, isovaleric acidemia, methylmalonic acidemia. Lysosmal storagc disorders identified were GM1 gangliosidosis, mucolipidosis II, Hurler, Hunter, Maroteaux-Lamy, Sialidosis (neuraminidase deficicncy), Sly, Scheie, Gaucher, Niemann-Pick, Sandhoff and many other neurodegeneraative disorders identified were rhizomelic chondrodysplasia punctata (RCDP) and Zellweger. Recently fatty acid oxidation disorders: MCAD, translocase deficiency and multiple carbosxylase deficiency 9biotinidase deficiency) were also identified.

Detection of inherited metabolic disorders via tandem mass spectrometry in Thai infants

From a retrospective study in Medical Genetics Unit, Department of Pediatrics, Siriraj Hospital Faculty of Medicine, Mahidol University in Bangkok (1983-1988), the estimated pediatric patients with clinically suspected IEM are approximately 2-4% of total annual pediatrics admission of 5,000 or more. This is, a low estimation since survey from all teaching hospitals in the country including the largest Children's Hospital in Bangkok indicated the presence of numerous IEM. However, most IEM were clinically diagnosed with limited laboratory facilities. We started a collaboration with Magee Womens Hospital of Pittsburgh and NeoGen Screening, USA; using tandem mass spectrometry to diagnose high risk infants and children for IEM from July 1993 to March 1998. Of total 146 samples sent, we detected numerous metabolic disorders (11.2%) eg phenylketonuria, organic acidemia, maple syrup urine disease, isovaleric acidemia, methylmalonic acidemia, albinism, translocase/carnitine palmitoyltransferase type II, G6PD deficiency and lysinuric protein intolerance.

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.

Medium-chain acyl-CoA dehydrogenase (MCAD) mutations identified by MS/MS-based prospective screening of newborns differ from those observed in patients with clinical symptoms: identification and characterization of a new, prevalent mutation that results in mild MCAD deficiency

Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is the most frequently diagnosed mitochondrial beta-oxidation defect, and it is potentially fatal. Eighty percent of patients are homozygous for a common mutation, 985A-->G, and a further 18% have this mutation in only one disease allele. In addition, a large number of rare disease-causing mutations have been identified and characterized. There is no clear genotype-phenotype correlation. High 985A-->G carrier frequencies in populations of European descent and the usual avoidance of recurrent disease episodes by patients diagnosed with MCAD deficiency who comply with a simple dietary treatment suggest that MCAD deficiency is a candidate in prospective screening of newborns. Therefore, several such screening programs employing analysis of acylcarnitines in blood spots by tandem mass spectrometry (MS/MS) are currently used worldwide. No validation of this method by mutation analysis has yet been reported. We investigated for MCAD mutations in newborns from US populations who had been identified by prospective MS/MS-based screening of 930,078 blood spots. An MCAD-deficiency frequency of 1/15,001 was observed. Our mutation analysis shows that the MS/MS-based method is excellent for detection of MCAD deficiency but that the frequency of the 985A-->G mutant allele in newborns with a positive acylcarnitine profile is much lower than that observed in clinically affected patients. Our identification of a new mutation, 199T-->C, which has never been observed in patients with clinically manifested disease but was present in a large proportion of the acylcarnitine-positive samples, may explain this skewed ratio. Overexpression experiments showed that this is a mild folding mutation that exhibits decreased levels of enzyme activity only under stringent conditions. A carrier frequency of 1/500 in the general population makes the 199T-->C mutation one of the three most prevalent mutations in the enzymes of fatty-acid oxidation.

Optimization of an automated DNA purification protocol for neonatal screening

CONTEXT

Collection of blood from newborns is a standard clinical procedure used for genetic screening. Typically, blood from a heel prick is absorbed onto standard collection paper and dried before analysis of metabolites, proteins, hormones, and more recently DNA.

OBJECTIVE

To evaluate strategies to purify DNA for use with automated workstations.

DESIGN

Two factors were used to evaluate several DNA purification protocols: residual heme contamination and amplification yield. The protocol that produced DNA with the lowest heme content and the highest amplification yield was selected. In combination with those two performance factors, the protocol with the fewest number of steps was chosen to reduce reagent use and processing time.

SETTING

Industrial research and development laboratory.

RESULTS

Robust amplification of DNA isolated from dried blood spots was demonstrated using both fluorescence and agarose gel-based detection methods. In addition, the samples had consistent DNA volumes and had no detectable cross-contamination. Suggested instrument settings, equipment, and supplies were included for automated processing of DNA from dried blood spots.

CONCLUSION

A 4-step DNA processing protocol was developed for dried blood spots. The protocol could be performed in either a manual or automated format, making it possible to process hundreds of samples in 1 day.

Laboratory integration and utilization of tandem mass spectrometry in neonatal screening: a model for clinical mass spectrometry in the next millennium

Clinical and neonatal screening methods using a tandem mass spectrometer are clearly a model for modern laboratory testing in the new Millennium. By the year 2000, more than 1 million blood and plasma samples will have been tested in laboratories throughout the world for a battery of metabolic disorders using a tandem mass spectrometer as the primary analytical device. A tandem mass spectrometer is considered the "ultimate" analytical detector in a variety of biochemical and clinical methods because of its very high accuracy, selectivity, precision, versatility and robust nature. The ability to achieve very high and reproducible sample throughput (approximately 600 samples/instrument/24 h) has made this technology cost-effective for newborn screening. In order to reliably measure markers of inborn errors of metabolism while maintaining low costs and high efficiency, accuracy and quality, much attention needs to be placed on monitoring and maintenance of all components of the entire testing system. These components include specimen collection and sample preparation methods, analysis by LC tandem mass spectrometry, conversion of raw mass spectra (data) into clinically meaningful results (concentration), expert interpretation of these results so that the clinician can be provided with information to facilitate a diagnose, and follow-up and education so that the maximum benefits of newborn screening translate into prevention of disease symptoms or more effective treatments. Addressing each part of the whole system will produce a quality screening program that will detect a battery of disorders using tandem mass spectrometry with a disease frequency of nearly 1 in 4000 infants.

DNA microarray technology for neonatal screening

Modern molecular biology, owing much to the Human Genome Initiative, has elucidated many of the genetic mechanisms underlying heritable metabolic disease. While the use of molecular methods has flourished in research laboratories, complexity and cost have limited their utility in newborn screening. Newborn blood cards provide high quality DNA samples able to provide reliable support to highly multiplexed polymerase chain reactions (PCR). New manufacturing processes have reduced the cost of DNA microarray technology to the point where it is a practical tool for population screening. In a single assay, a DNA microarray facilitates the co-detection of amplification products diagnostic for several genetic diseases. High throughput is achieved with automation at every step, from DNA extraction to detection of hybrids. We suggest that it is both feasible and practical to develop a first-tier newborn screening protocol based upon multiplex PCR and analysis of amplification products using DNA microarrays. Initial data utilizing the model systems of sickle cell disease, alpha-1-antitrypsin deficiency and Factor V Leiden will be reported.

Automated tandem mass spectrometry for mass newborn screening for disorders in fatty acid, organic acid, and amino acid metabolism

Development of acylcarnitine and amino acid profiling using tandem mass spectrometry, and its application for use with dried blood specimens collected on filter-paper cards, has introduced an innovative new technology for detecting inborn errors of fatty acid, organic acid, and amino acid metabolism. From November 1, 1992 through June 30, 1999 we screened more than 700,000 newborns in Pennsylvania, Ohio, North Carolina, and Louisiana. We have prospectively detected 163 inborn errors of metabolism. Eighty-six patients have amino acid metabolism errors. Among them are phenylketonuria, hyperphenylalaninemia, maple syrup urine disease, and several urea cycle disorders. Thirty-two have organic acid metabolism errors, including glutaric aciduria type 1; 3-methylcrotonyl coenzyme A (CoA) carboxylase deficiency, propionic acidemia, methylmalonic acidemia, and 3-hydroxy-3-methylglutaryl-CoA lyase deficiency; and 45 have fatty acid oxidation errors, including 36 with medium-chain acyl-CoA dehydrogenase deficiency. Details of the methodology are presented and the potential of this screening technology is discussed.

Immunoreactive trypsinogen levels in pediatric patients with intestinal failure awaiting intestinal transplantation

The aim of this study was to evaluate pancreatic function in total parenteral nutrition (TPN)-dependent children with permanent intestinal failure by measuring immunoreactive trypsinogen (IRT) levels. Between 1992 and 1996, 105 pediatric patients with permanent intestinal failure were referred to the Children's Hospital of Pittsburgh for small intestinal transplant evaluation. Serum samples were available from 55 of them. Ten suffered from intestinal pseudo-obstruction or microvillus inclusion disease, while 45 had short bowel syndrome (SBS). IRT levels were significantly higher (p < 0.001) in SBS patients (89.4 +/- 9.2 ng mL) compared to controls (43.4 +/- 5.6 ng/ nL) without liver, gastrointestinal, or kidney disease. IRT levels did not correlate with liver injury, length of bowel, or the cause of SBS. Five of 20 patients who underwent intestinal transplantation developed pancreatitis during a median post-operative follow up 15.4 months later. IRT levels failed to predict who would develop pancreatitis post-transplant. The data suggest that elevated plasma IRT levels are common among children with intestinal failure, but fail to identify patients at risk for pancreatitis post-transplant.

3-Methylcrotonyl-coenzyme A carboxylase deficiency in Amish/Mennonite adults identified by detection of increased acylcarnitines in blood spots of their children

Isolated 3-methylcrotonyl coenzyme A carboxylase (MCC) deficiency was documented in four adult women from the Amish/Mennonite population of Lancaster County, Pennsylvania. Metabolic and enzymatic investigations in these individuals were instituted after the detection of abnormal acylcarnitine profiles in blood spots obtained from their newborn children, in whom MCC activity was normal.

Rapid diagnosis of MCAD deficiency: quantitative analysis of octanoylcarnitine and other acylcarnitines in newborn blood spots by tandem mass spectrometry

We report the application of tandem mass spectrometry to prospective newborn screening for medium-chain acyl-CoA dehydrogenase (MCAD) deficiency. MCAD deficiency is diagnosed from dried blood spots on filter paper cards from newborns on the basis of the increase of medium chain length acylcarnitines identified by isotope dilution mass spectrometry methods. A robust and accurate semiautomated method for the analysis of medium chain length acylcarnitines as their butyl esters was developed and validated. Quantitative data from the analyses of 113 randomly collected filter paper blood spots from healthy newborns showed low concentrations of medium chain length acylcarnitines such as octanoylcarnitine. The maximum concentration of octanoylcarnitine was 0.22 mumol/L, with the majority being at or below the detection limit. In all 16 blood spots from newborns with confirmed MCAD deficiency, octanoylcarnitine was highly increased [median 8.4 mumol/L (range 3.1-28.3 mumol/L)], allowing easy detection. The concentration of octanoylcarnitine was significantly higher in these 16 newborns (< 3 days of age) than in 16 older patients (ages 8 days to 7 years) with MCAD deficiency (median 1.57 mumol/L, range 0.33-4.4). The combined experience of prospective newborn screening in Pennsylvania and North Carolina has shown a disease frequency for MCAD deficiency of 1 in 17,706. No false-positive and no known false-negative results have been found. A validated method now exists for prospective newborn screening for MCAD deficiency.

Direct analysis of filter paper blood specimens for identification of Smith-Lemli-Opitz syndrome using time-of-flight secondary ion mass spectrometry

In this study, time-of-flight secondary ion mass spectrometry was used to distinguish between blood of normal infants and that of individuals with Smith-Lemli-Opitz (SLO) syndrome. SLO syndrome results in an abnormally low concentration of blood cholesterol and an elevated concentration of 7-dehydrocholesterol. Blood was spotted on filter paper and analyzed directly with no extractions or separations. Results showed that using ratios of fragment ions for cholesterol/dehydrocholesterol, patients with SLO and normal individuals could be unambiguously distinguished. Unknown samples from 28 individuals were obtained and identified correctly.

Immediately elevated postoperative serum branched-chain amino acids following effective GI decompression and enteral feeding

Postoperative patients are hypercatabolic. They also suffer a degree of gastrointestinal (GI) dysfunction impairing nutritional intake. Safe enteral absorption had been limited to a maximum of 500 kcal provided over the initial 24 h in all previously reported regimens. Several days of negative nitrogen balance and diminution of serum branched-chain amino acids (BCAA) result. Some data suggest an association with suboptimal wound healing, and immune competence. We tested the hypothesis that immediate exploitation of more effectively preserved GI function could prevent this depressed serum concentration within hours of surgery. Our study group consisted of 34 consecutive elective "open" cholecystectomy patients who had terminal esophageal, gastric, and proximal duodenal decompression. Simultaneous distal duodenal feeding of elemental diet began immediately in the Recovery Room at 300 mL/h for 8-16 h, providing 2,400-4,800 kcal and 100-200 g amino acids. We found that each serum BCAA concentration rose above basal by one hour. The differences reached statistical significance (p < or = 0.05) within 2 h after surgery, when leucine had risen above basal levels by 70%, isoleucine by 63%, and valine by 26%. Elevations in these BCAA serum concentrations persisted for the duration of feeding. GI function can be maintained and successfully utilized in the immediate postoperative period for absorption of 300 kcal/h. Postoperative depression of serum BCAA concentrations are prevented. The serum BCAA rise of these GI protected and immediately fed postoperative patients contrasts with the 48-72 h decline universally reported with conventional protein- and calorie-deficient regimens. The optimum nutritional regimen for achievement of clinically significant enhanced wound healing, sepsis resistance, and muscle sparing, remains to be determined.

Medium chain acyl-CoA dehydrogenase deficiency in Pennsylvania: neonatal screening shows high incidence and unexpected mutation frequencies

Medium chain acyl-CoA dehydrogenase deficiency (MCAD) is a defect in the mitochondrial oxidation of fatty acids. The disorder typically presents with episodes of vomiting and hypoglycemia, sometimes with changes in mental status and hepatic failure. These Reye's-like features may culminate in coma and death. Stress, intercurrent illness, and reaction to childhood immunization have been shown to precipitate acute metabolic episodes in MCAD patients. All cases are caused by mutations of the single MCAD gene on chromosome 1. Most clinically ascertained cases are caused by an A985G transition in exon 11. Here we report the preliminary findings of MCAD patients detected prospectively through a supplemental newborn screening program in Pennsylvania using tandem mass spectrometry. From the first 80,371 newborns screened we prospectively found nine babies with MCAD (1/8930) plus two additional newborns screened because of a previously known family history. Molecular analysis showed 56% of the detected patients to be compound heterozygotes for the A985G and a second mutation. This is in contrast to clinical retrospective studies which have found only 20% to be compound heterozygotes. We have identified two of the other mutations including a novel mutation (DG91/C92, 6-bp deletion) in one of our patients by using single-stranded conformation polymorphism (SSCP) and sequence analysis of conformers. Our results confirm that MCAD is one of the more common inborn errors of metabolism. The different mutation frequencies observed between retrospective clinical studies and our prospective newborn screening study suggest that clinical ascertainment may lead to preferential identification of the A985G mutation.

Rapid diagnosis of maple syrup urine disease in blood spots from newborns by tandem mass spectrometry

We report a new method for the diagnosis of maple syrup urine disease (MSUD) from dried blood spots on newborn screening cards based on tandem mass spectrometry (MS-MS). The mean +/- SD concentration of Leu plus Ile in normal newborns was 151 +/- 47 mumol/L (n = 1096); for Val, 131 +/- 58 mumol/L (n = 791). SDs were lower when the concentrations of these amino acids were expressed relative to that of Phe. The mean ratio for Leu + Ile to Phe was 2.5 +/- 0.49; for Val to Phe, 2.18 +/- 0.51. These results compare well with values previously reported in the literature. With these criteria, samples from a collection categorized by a bacterial inhibition assay as normal or falsely positive for MSUD were normal by MS-MS [(Leu + Ile): Phe &lt; 5.0]. Samples from confirmed MSUD patients were categorized as abnormal [(Leu+Ile): Phe &gt; 9.0] by MS-MS.

Rapid diagnosis of maple syrup urine disease in blood spots from newborns by tandem mass spectrometry

We report a new method for the diagnosis of maple syrup urine disease (MSUD) from dried blood spots on newborn screening cards based on tandem mass spectrometry (MS-MS). The mean +/- SD concentration of Leu plus Ile in normal newborns was 151 +/- 47 mumol/L (n = 1096); for Val, 131 +/- 58 mumol/L (n = 791). SDs were lower when the concentrations of these amino acids were expressed relative to that of Phe. The mean ratio for Leu + Ile to Phe was 2.5 +/- 0.49; for Val to Phe, 2.18 +/- 0.51. These results compare well with values previously reported in the literature. With these criteria, samples from a collection categorized by a bacterial inhibition assay as normal or falsely positive for MSUD were normal by MS-MS [(Leu + Ile): Phe < 5.0]. Samples from confirmed MSUD patients were categorized as abnormal [(Leu+Ile): Phe > 9.0] by MS-MS.

Mutation in the 4a-carbinolamine dehydratase gene leads to mild hyperphenylalaninemia with defective cofactor metabolism

Hyperphenylalaninemias represent a major class of inherited metabolic disorders. They are most often caused by mutations in the phenylalanine hydroxylase gene and, less frequently but with usually more serious consequences, in genes necessary for the synthesis and regeneration of the cofactor, tetrahydrobiopterin. This cofactor is absolutely required for all aromatic amino acid hydroxylations, and, recently, nitric oxide production from L-arginine has also been found to be dependent on tetrahydrobiopterin. Phenylalanine hydroxylase catalyzes a coupled reaction in which phenylalanine is converted to tyrosine and in which tetrahydrobiopterin is converted to the unstable carbinolamine, 4a-hydroxytetrahydrobiopterin. The enzyme, carbinolamine dehydratase, catalyzes the dehydration of the carbinolamine to quinonoid dihydropterin. A decreased rate of dehydration of this compound has been hypothesized to be responsible for the production of 7-biopterin found in certain mildly hyperphenylalaninemic individuals. We have now identified nonsense and missense mutations in the 4a-carbinolamine dehydratase gene in a hyperphenylalaninemic child who excretes large amounts of 7-biopterin. This finding is consistent with the role of the carbinolamine dehydratase in the phenylalanine hydroxylation reaction. Together with previously identified inherited disorders in phenylalanine hydroxylase and dihydropteridine reductase, there are now identified mutations in the three enzymes involved in the phenylalanine hydroxylation system. In addition, the genetics of this system may have broader implications, since the product of the dehydratase gene has previously been shown to play an additional role (as dimerization cofactor for hepatocyte nuclear factor-1 alpha) in the regulation of transcription, through interaction with hepatocyte nuclear factor-1 alpha.

Neonatal screening for cystic fibrosis: addition of molecular diagnostics to increase specificity

Newborn screening for cystic fibrosis (CF) has been carried out on approximately 106,000 neonates in western Pennsylvania since 1987 using the immunoreactive trypsinogen (IRT) assay on dried filter paper blood specimens (DBS). Molecular analysis utilizing a duplicate DBS from the same sample was implemented in November 1989 for newborns having elevated IRT levels. DNA is amplified directly from the DBS and the amplified products are tested for the delta F508 deletion and several common exon 11 mutations. Substituting dUTP for dTTP in the PCR reaction and an initial treatment with uracil N-glycosylase (UNG) virtually eliminates PCR carryover contamination. The number of confirmed cases of CF is 20, giving an estimated incidence of 1:5287 in the western Pennsylvania population. Eight of the CF patients are homozygous and 12 are compound heterozygotes for the delta F508 deletion and a second mutation. Two of the compound heterozygotes carry the G551D mutation and one has the R553X mutation. Twenty-one additional neonates that are heterozygous for the delta F508 mutation are normal carriers for CF. In approximately 55% of the cases, molecular analysis of the CF gene confirmed the diagnosis of CF prior to sweat testing. The incorporation of molecular analysis into our CF screening program increases the specificity of the screening strategy and has the potential to decrease the false positive and sweat test referral rate, reduce parental anxiety, and bring CF infants to the attention of physicians more rapidly.

New technologies in newborn screening

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Repetitive recycling of guanosine triphosphate cyclohydrolase I for synthesis of dihydroneopterin triphosphate

A procedure for enzymatic production of dihydroneopterin triphosphate is described that allows GTP cyclohydrolase I to be reused repetitively. The reaction takes place in an ultrafiltration cell, and the product is collected in the filtrate, whereas the enzyme remains in the cell to be reused with additional substrate. This is repeated until the enzyme activity drops below a desirable level. The purity of the dihydroneopterin triphosphate is satisfactory for utilization of this compound for studies on enzymes involved in the synthesis of tetrahydrobiopterin and drosopterin. A procedure for purification of dihydroneopterin triphosphate is described that uses C18-silica and silica cartridges.

Sepiapterin reductase in human amniotic and skin fibroblasts, chorionic villi, and various blood fractions

Sepiapterin reductase activity has been measured in amniotic fibroblasts by two procedures: one photometric and the other HPLC-fluorimetric. Both can be used for quantitative measurements, but the latter has considerable advantages including smaller standard deviation, much lower detection limit, and less volume of sample required. Sepiapterin reductase activity was also assayed in skin fibroblasts, chorionic villi and various blood fractions including stimulated mononuclear blood cells. Red blood cells have a low specific activity compared to unstimulated mononuclear blood cells, although the latter have a mean value with a high standard deviation. When the mononuclear blood cells were cultured for 5 days, the mean specific activity increased and the range became tighter. Enzyme stability and N-acetylserotonin inhibition were also studied.

Sepiapterin reductase in cultured human cells

Sepiapterin reductase, an enzyme involved in the synthesis of tetrahydrobiopterin (the natural cofactor for phenylalanine, tyrosine and tryptophan hydroxylases), has been assayed in cultured human amniotic fibroblasts and in cultured mononuclear blood cells. In both cases, the Michaelis constants for sepiapterin and NADPH were essentially equal; 20 microM and 6 microM respectively for stimulated mononuclear blood cells and 22 microM and 5 microM respectively for amniotic fibroblasts. The inhibition by N-acetylserotonin was also similar in both cases. The concentration that produced 50% inhibition in stimulated mononuclear blood cells and in amniotic fibroblasts was 2 microM. The results strongly suggest that the same enzyme is acting in both types of cells, at least when grown in culture.

Guanosine triphosphate cyclohydrolase I deficiency: early diagnosis by routine urine pteridine screening

A deficiency of hepatic guanosine triphosphate cyclohydrolase I is reported in a 4-month-old infant in whom positive results on a Guthrie phenylketonuria test in the neonatal period were found. Because of the significantly elevated serum phenylalanine levels a diagnosis of classical phenylketonuria was made, and dietary therapy was started. Urinary pteridine screening for cofactor variants, however, revealed extremely low levels of both neopterin and biopterin. This suggested the possibility of guanosine triphosphate cyclohydrolase I deficiency and led to additional confirmatory assays. Repeat urine, serum, and CSF pteridine profiles, combined with tetrahydrobiopterin-loading studies and the assay of guanosine triphosphate cyclohydrolase I activity in a liver biopsy, confirmed the defect. It is significant to note that the diagnosis was made before the onset of major clinical symptoms. This case illustrates the need for routine cofactor variant screening of all infants in whom hyperphenylalaninemia is diagnosed in the neonatal period.

Plasma phenylethylamine and phenylalanine in chronic schizophrenic patients

The hypothesis that phenylethylamine (PEA) is an endogenous psychotogen in schizophrenics, particularly those with the paranoid subtype, has been previously studied by measuring PEA levels in urine and cerebrospinal fluid (CSF) of schizophrenic patients. However, plasma PEA may more accurately reflect simultaneous alterations of PEA in many organ systems, as might occur in a genetic disorder of PEA metabolism. No study to date has examined phenylalanine (Phe), which is thought to be a precursor of PEA, in the same patients who had PEA measured. In this study, we measure both plasma PEA and Phe in 17 drug-free schizophrenic patients and 17 matched controls. Plasma PEA in normal controls was found to be lower by three orders of magnitude compared to normal controls from previous studies--a finding that has not previously been reported. PEA was significantly lower in those schizophrenic patients who had a Research Diagnostic Criteria diagnosis of paranoid schizophrenia. PEA did not differ between patients and controls, and the correlation between plasma Phe and PEA was not significant.

Dihydropteridine reductase in schizophrenic patients

The activity of the enzyme dihydropteridine reductase (DHPR) has been recently found to be one of the factors controlling the rate of synthesis of dopamine, norepinephrine, and serotonin, thought to be involved in the etiology of schizophrenia. Several lines of evidence suggest that peripheral and brain DHPR enzymes may be identical. In addition, peripheral DHPR activity has been hypothesized to be important in determining the level of phenylethylamine, a putative psychotogen that is produced peripherally and crosses the blood-brain barrier. Since DHPR activity has never been investigated in schizophrenic patients, we measured the whole blood activity in 20 schizophrenic patients and 20 matched controls. There was no difference between the groups in DHPR activity.

Simplified procedure for producing Bacillus subtilis spores for the Guthrie phenylketonuria and other microbiological screening tests

Bacillus subtilis ATCC 6051 and ATCC 6633 spores used in bacterial inhibition screening assays for genetic metabolism defects in newborn infants were produced by using liquid synthetic replacement sporulation media. These media allowed a high degree of sporulation, as judged by direct cell counts. Sporulation took place within 23 to 27 h with these media. Also, a more rational procedure for selecting the most sensitive clones of these organisms to the various inhibitors used in the microbiological screening assays is presented.

A rapid screening test for Duchenne muscular dystrophy using dried blood specimens

A very simple fluorescent spot screening test for the detection of elevated creatine kinase activity in dried blood specimens is described. The assay uses reagents commercially available in kit form and modifies the procedure for use with whole blood spotted on filter paper. Additional amounts of diadenosine pentaphosphate had to be added to the reaction mixture to inhibit the excess adenylate kinase present in erythrocytes. The sensitivity and reliability of the test is demonstrated. This qualitative assay has the potential for use as a mass neonatal screening test for Duchenne muscular dystrophy.

A neonatal screening test for argininosuccinic acid lyase deficiency and other urea cycle disorders

A simple enzyme-multiple auxotroph assay has been developed for the identification of newborn infants with several of the inherited metabolic defects in the Krebs cycle for the detoxification of ammonia and in the ornithine metabolic pathway. This mass screening test is used with dried filter paper blood specimens and can easily be added to existing multiple testing programs presently used in screening for phenylketonuria or congenital hypothyroidism. This assay can be used to detect patients with citrullinemia, argininosuccinic acid lyase deficiency, and argininemia. In addition to these urea cycle disorders, the several types of ornithinemia, which can result in gyrate atrophy of the retina or mental retardation, should be detectable with this assay. The strengths and weaknesses of this assay are discussed and a large-scale pilot screening trial is proposed.

Screening test for alpha 1-antitrypsin in dried-blood specimens

We describe a fluorescent spot test for detecting alpha 1-antitrypsin activity in dried-blood specimens. The eluate of a blood disc is mixed with carbobenzoxy-L-arginine-7-amino-4-methylcoumarin amide and trypsin at the appropriate pH. In the absence of alpha 1-antitrypsin, aminomethylcoumarin, a strongly fluorescent compound, is released. The reaction mixture, when spotted on chromatography paper and viewed under ultraviolet light, exhibits a bright fluorescence only in the case of specimens with alpha 1-antitrypsin deficiency. alpha 1-Antitrypsin activity so estimated correlated well with quantitative assays of dried-blood spots and serum. The procedure is simple and inexpensive, and has the potential for use as a screening test.

Screening test for alpha 1-antitrypsin in dried-blood specimens

We describe a fluorescent spot test for detecting alpha 1-antitrypsin activity in dried-blood specimens. The eluate of a blood disc is mixed with carbobenzoxy-L-arginine-7-amino-4-methylcoumarin amide and trypsin at the appropriate pH. In the absence of alpha 1-antitrypsin, aminomethylcoumarin, a strongly fluorescent compound, is released. The reaction mixture, when spotted on chromatography paper and viewed under ultraviolet light, exhibits a bright fluorescence only in the case of specimens with alpha 1-antitrypsin deficiency. alpha 1-Antitrypsin activity so estimated correlated well with quantitative assays of dried-blood spots and serum. The procedure is simple and inexpensive, and has the potential for use as a screening test.

Neonatal urine screening for metabolic disease with auxotrophic strains of Bacillus subtilis

A simplified method for neonatal urine screening for metabolic diseases is described. This procedure involves the use of two bacterial inhibition assays which can detect uracil, lysine, and homocystine, in combination with two other assays utilizing spores of amino acid auxotrophic mutants of Bacillus subtilis which can detect several amino acids and purines. These four tests have the capability to detect several treatable inherited metabolic diseases, including three disorders of the urea cycle, using a urine specimen on filter paper. This method results in savings of cost and time over chromatographic screening procedures, since only four agar trays (56 specimens per tray) are used, which can be processed with one cycle through a semi-automated punch index machine.

Adrenal adenomas in a patient with Gardner's syndrome

Gardner's syndrome is an autosomal dominant condition characterized by multiple colorectal polyposis, associated with various soft- and hard-tissue tumors. The occurrence of adrenal adenomas in patients with the syndrome has not been fully appreciated. The following is a report of a member of the original Utah kindred #109, first described in the early 1950's who was found at autopsy to have bilateral adrenal adenomas. A review of the literature resulted in the identification of six cases with adrenal adenomas and one with a primary adrenal carcinoma. The association with the syndrome of these adrenal tumors, as well as other endocrine tumors, especially thyroid tumors, is discussed.

Urinary pyrimidine excretion in arginase deficiency

A high-performance liquid-chromatographic method was used to separate and identify uracil, uridine, pseudouridine and orotic acid after preliminary extraction in two patients (McKusick 20780). Urinary uracil excretion was 10-35 times normal in both patients with arginase deficiency. Uridine and orotic acid, not normally detected, were excreted in large amounts and were directly influenced by protein intake. Their excretions were correlated with urinary arginine excretion. Urinary uracil levels remained consistently high and showed minimal variations with increased protein intake or urinary arginine levels. The measurement of urinary pyrimidines appears to be useful for the detection, differential diagnosis and dietary monitoring of patients with urea cycle disorders. The data presented extends this observation to include patients with arginase deficiency.

Gardner's syndrome. Recent developments in research and management

In recent years, a number of comprehensive reviews have been written on inherited intestinal polyposis syndromes (1-7), but none has dealt specifically with Gardner's syndrome and none has focused on basic research being carried out in an attempt to understand this syndrome and to improve the medical management of affected patients. A better understanding of this rare genetic disorder is essential for surgeons, gastroenterologists, cancer researchers, and geneticists alike. To the clinician, it poses difficult challenges in management; to the cancer researcher, it presents a rare opportunity to study very early premalignant transformations; and to the geneticist, it poses exciting questions at the cellular, chromosomal, and molecular levels.

Fluorometric micromethod for determination of arginase activity in dried blood spots on filter paper

We describe a microfluorometric method for determination of arginase activity in dried blood spots on filter paper. The arginase in discs punched from such dried blood specimens is activated by preincubation with Mn2+ at 37 degrees C. After incubation with substrate at the same temperature, urea is determined fluorometrically by oxidation of NADH to NAD+ in a coupled kinetic reaction. We compare the results of this method with those of a colorimetric method involving liquid blood samples, and assess the stability of the enzyme in dried blood on filter paper. The presence of serum has no effect on the activity. This method may be useful in the early detection of arginase deficiency and certain hematological disorders.

Fluorometric micromethod for determination of arginase activity in dried blood spots on filter paper

We describe a microfluorometric method for determination of arginase activity in dried blood spots on filter paper. The arginase in discs punched from such dried blood specimens is activated by preincubation with Mn2+ at 37 degrees C. After incubation with substrate at the same temperature, urea is determined fluorometrically by oxidation of NADH to NAD+ in a coupled kinetic reaction. We compare the results of this method with those of a colorimetric method involving liquid blood samples, and assess the stability of the enzyme in dried blood on filter paper. The presence of serum has no effect on the activity. This method may be useful in the early detection of arginase deficiency and certain hematological disorders.

Enzymatic studies of urinary isomeric chondroitin sulfates from patients with mucopolysaccharidoses. The application of high performance liquid chromatography

The high-performance liquid chromatographic (HPLC) method for the determination of unsaturated sulfated disaccharides is a comprehensive and reliable method which expedites ensymatic studies of isomeric chondroitin sulfates. Responses for these unsaturated disaccharides derived from urinary chondroitin sulfates were linear from 100 ng to 10 micrograms injected and good quantitation was obtained for 25 microliters or less of samples placed on the column. This method which is more sensitive and accurate than methods now being used has considerable potential for the chemical diagnosis of patients with mucopolysaccharidoses and for the clarification of glycosaminoglycan structure. The isomeric chondroitin sulfates in urines from patients with mucopolysaccharidoses were studied by enzyme digestion with chondroitinases followed by HPLC determination of the sulfated unsaturated disaccharides produced. Evaluation by HPLC of the unsaturated 4-sulfated disaccharide produced by digestion of the urinary GAG with chondroitinases ABC and AC revealed rapidly and quantitatively the large amounts of dermatan sulfate present in Hurler, Hunter, and Maroteaux-Lamy urines. Chondroitin 4-sulfate predominated in Sanfilippo urinary isomeric chondroitin sulfates whereas chondroitin 6-sulfate and chondroitin 4-sulfate were shown to be present in nearly equal amounts in Morquio urine. An oversulfated chondroitin sulfate was detected in small amounts in some of these urines. This was demonstrated by the detection of an unsaturated disulfated disaccharide after digestion with chondroitinase ABC but not with chondroitinase AC.