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Neonatal screening for congenital hypothyroidism in Mexico: experience, obstacles, and strategies.

OBJECTIVE: To report the experience, obstacles, and strategies of screening for congenital hypothyroidism. SETTING: Newborns in Mexico. METHODS: Thyroid stimulating hormone (TSH) was measured by enzyme immunoassay using commercial kits in 1,140,364 newborns. RESULTS: There were 464 positive cases, of whom 299 (64.4%) were girls. 236 (50.9% showed ectopic nodules, 202 (43.5%) thyroid agenesis, 21 (4.5%) dyshormonogenesis, and 5 (1.1%) an unclassified goitre. The false positive rate was 0.024% and there were 11 false negative results. Currently, 600,000 (26%) of the 2,300,000 newborns are screened. This percentage has been increased in recent years by taking samples from cord blood and will be increased further by starting congenital hypothyroidism screening at social security units and by midwives screening infants born at home. CONCLUSIONS: Mental retardation in infants in developing countries can be reduced by neonatal screening, and carefully planned strategies can steadily extend the benefits of screening.

Blood Specimen Collection↗

A pilot study for neonatal screening of congenital adrenal hyperplasia due to 21-hydroxylase and 11-beta-hydroxylase deficiency in Campania region.

A neonatal screening for both 21-hydroxylase and 11-beta-hydroxylase deficiencies, responsible for congenital adrenal hyperplasia (CAH), has been conducted in Campania Region, Southern Italy. In 4380 neonates, aged 2-10 days, capillary blood from a heel prick was collected on microfilter paper, and 17-alpha-hydroxyprogesterone (17OHP) measured by radioimmunoassay (RIA) using a highly specific antibody (Ab A). In addition, in 295 of these samples, both 17OHP and 11-deoxycortisol (S) were measured using an anti-deoxycortisol antibody (Ab B) cross-reacting with 17OHP 100%. All results were compared with plasma 17OHP and S levels in 21 patients with diagnosed 21-hydroxylase deficiency and in 5 healthy volunteers on metyrapone test used for blocking the 11-beta-hydroxylase activity. CAH due to 21-hydroxylase deficiency was diagnosed in a female newborn. The assay, based on the antibody reacting with both 17OHP and S, is particularly suitable for wide-scale screening programs enabling the simultaneous detection of two congenital enzyme defects.

Adolescent↗

Linear growth in children with congenital hypothyroidism detected by neonatal screening and treated early: a longitudinal study.

We performed a longitudinal study of a cohort of 74 children with congenital hypothyroidism (CH) detected by neonatal screening (Buenos Aires Province, Argentina) up to the age of 3 years old, in order to study linear growth and the relationship with the severity of CH at diagnosis. The mean age at diagnosis and the start of the treatment was 16.9 +/- 5.2 days. The patients were divided into group 1--severe CH (pretreatment T4 level <4 microg/dl) (n = 47)--and group 2--less severe CH (pretreatment T4 level > or = 4 microg/dl) (n = 27). Patients with CH treated early showed a sexually dimorphic pattern of growth: girls tended to be longer than boys at all ages. Boys showed some delay of growth during the first year. No difference was found in linear growth between the two groups (more/less severe CH). Height was normal in both sexes at the age of 3 years old.

Child Development↗

Neonatal screening for defects of the mitochondrial trifunctional protein.

Long-chain l-3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency has been included in the routine neonatal screening program by the German screening commission. As tandem mass spectrometry (TMS) does not discriminate between the different defects of the mitochondrial trifunctional protein (MTP) screening for isolated LCHAD deficiency includes the detection of long-chain 3-ketoacyl-CoA thiolase and complete MTP deficiencies as well. We identified 11 patients with abnormalities of the MTP out of 1.2 million newborns screened in our laboratory during the last 6 years. Treatment was started on the day the screening result was obtained (day 3 to day 9 of life). Seven of these newborns developed satisfactorily during an observation period of up to 64 months. They had isolated LCHAD deficiency, four of them caused by the typical mutation (1528 G>C), three others had no molecular genetic analysis done or were shown to have previously unknown mutations. Four children did not survive, two of them showing complete deficiency of MTP and two showing deficiency of long-chain 3-ketoacyl-CoA thiolase. We conclude that, despite the rarity of the disease, screening for MTP deficiencies is justified based on the following criteria: improved quality of life for patients with isolated LCHAD deficiency, absence of stigmatisation of babies showing mild variants without necessity of treatment, no significant increase of the total number of false positive screening results, no false negative results to our knowledge. Finally, extension of analysis to MTP deficiencies is achieved without additional costs for screening laboratories already using TMS.

3-Hydroxyacyl CoA Dehydrogenases↗

[Progress in neonatal screening for genetic diseases of metabolism].

The main inborn errors of metabolism are described and the methods used for their screening. The recent technical progress in the screening tests are envisaged as well as the diagnosis and treatment aspects, insisting upon the fact that the neonatal screening undertaken in this areas are of vital importance, since the treatment of a number of specific inborn errors of metabolism constitutes a main trait of actual preventive pediatrics.

Humans↗

Neonatal screening for congenital hypothyroidism based on thyroxine, thyrotropin, and thyroxine-binding globulin measurement: potentials and pitfalls.

CONTEXT: The Dutch T(4)-TSH-TBG-based neonatal screening program detects patients with congenital hypothyroidism (CH) of thyroidal (CH-T) as well as central (CH-C) origin. The numbers and characteristics of true-positive and false-positive referrals will differ from other, predominantly TSH-based, screening methods. OBJECTIVE: The present study describes the characteristics of the referred neonates, both CH patients and false positives, and of the reported CH patients with a false-negative screening result born in the study period. DESIGN, SETTING, PATIENTS, AND MAIN OUTCOME MEASURE: For each referred child born between April 1, 2002, and May 31, 2004, screening results and first venous sample results were recorded and classified as transient or permanent CH-T or CH-C or as no CH. RESULTS: In the study period, 430,764 children were screened. Of the 772 children with abnormal screening results, 224 (29%) had CH; another 13 CH patients did not have abnormal screening results, giving an overall CH incidence of 1:1800. Incidences of permanent CH, permanent CH-T, permanent CH-C, and transient CH were 1:2200, 1:2500, 1:21,000, and 1:12,000, respectively. The most frequent explanations for the 548 false-positive referrals (71% of the referred cohort) were severe illness and TBG deficiency (occurring in 198 and 200 children, respectively). CONCLUSIONS: The Dutch incidence figures for CH belong to the highest worldwide, suggesting that the T(4)-TSH-TBG screening program is an efficient method to detect CH of variable etiology and severity. Still, a small percentage of children with CH escaped detection via this screening approach. Severe illness and TBG deficiency appear to be responsible for the majority of false-positive referrals.

Congenital Hypothyroidism↗

Carnitine in dried blood spots: a method suitable for neonatal screening.

A method is described which enables the quantitative determination of both free and total carnitine levels in dried blood spots. This method is suitable for neonatal screening for either primary or secondary carnitine deficiency. The 95% confidence interval for free carnitine was 26-76 mumol/l (median = 44) and for total carnitine was 35-102 mumol/l (median = 60).

Carnitine↗

Changing performance of the Health Visitor Distraction Test when targeted neonatal screening is introduced into a health district.

The change in the performance of the HVDT as targeted neonatal hearing screening has been introduced has been examined for the Nottingham district. The records for all children born in the period 1984-1993 within the district and having a permanent hearing loss of > or = 50 dB in the better ear have been examined. The referral route leading to ascertainment of the hearing loss as well as the result of any screening tests were noted. The data shows an increase in the number referred prior to the HVDT, mainly as a result of neonatal screen failure. At the same time there has been a reduction in the sensitivity of the HVDT from 78% in the first half of the decade to 38% for the second half. There are also some indications of an increase in the coverage and the failure rate over the time. Possible reasons for these changes are discussed.

Evoked Potentials, Auditory, Brain Stem↗

Relationship of genotype to early pulmonary function in infants with cystic fibrosis identified through neonatal screening.

To determine whether pulmonary function in infants with asymptomatic cystic fibrosis is related to genotype, we studied 18 infants with cystic fibrosis identified through neonatal screening and 18 healthy control infants. Infants with cystic fibrosis (mean age, 2.0 months; range, 1.0 to 4.6 months) were identified from June 1990 to September 1991 through a statewide screening program based on elevated immunoreactive trypsinogen concentrations. Pulmonary function testing was done before and after inhalation of albuterol. There were no differences in pulmonary function between the cystic fibrosis group and the control infants (mean age, 2.7 months; range, 0.9 to 4.5 months). However, infants homozygous for the delta F508 deletion (n = 10) differed from infants with other genotypic variants of cystic fibrosis and control infants with respect to respiratory system resistance (79.4 +/- 11.5 vs 52.0 +/- 3.8 vs 55.5 +/- 5.0 cm H2O/L per second, respectively; p = 0.04) and specific conductance (0.15 +/- 0.02 vs 0.21 +/- 0.02 vs 0.21 +/- 0.02 cm H2O-1 sec-1, respectively; p = 0.02). Infants homozygous for the delta F508 deletion, but not other infants, responded to albuterol with a decrease in respiratory system resistance. We conclude that infants with asymptomatic cystic fibrosis homozygous for the delta F508 deletion have early evidence of airways obstruction and may need early respiratory treatment.

Cystic Fibrosis↗

Is saliva as reliable as urine for detection of cytomegalovirus DNA for neonatal screening of congenital CMV infection?

BACKGROUND: There are no studies on the detection of cytomegalovirus (CMV) DNA by molecular methods in the saliva of newborn infants in large scale screening programs. OBJECTIVES: To evaluate the usefulness of saliva as a sample for the neonatal screening of congenital CMV infection as compared to urine when processed by a PCR. STUDY DESIGN: Saliva and urine samples were obtained during the first week of life. Both samples were attempted to be obtained from the first 2816 neonates. Subsequently, only saliva was obtained from other 1623 infants. Urine and saliva were processed by DNA-PCR. Confirmation of positive results was done by PCR and virus isolation by 3 weeks after birth. RESULTS: A urine sample was not obtainable from 893/2816 (31.7%) infants. Both saliva and urine samples were obtained from the remaining 1923 infants. Of these, 28 (1.45%) were CMV-infected. There was 99.7% agreement between the results with both samples. CMV excretion was similar when PCR was applied to urine (1.3%) or to saliva (1.2%) samples. Among the subsequent 1623 infants for whom only a saliva sample was planned for screening, 16 (0.98%) were CMV-infected. CONCLUSIONS: Saliva samples are as useful as urine for the identification of CMV-DNA in large use for screening programs.

Cytomegalovirus↗

[Results of a pilot study of neonatal screening for congenital biotinidase deficiency].

Biotinidase activity was determined in a pilot study of 78,000 dried blood samples on filter paper. In the assay the liberation of p-aminobenzoic-acid from biotinyl-p-aminobenzoic-acid by biotinidase is tested. One boy was identified to be with biotinidase deficiency. Transient reduction of biotinidase activity to virtually negative test results was observed in 8 preterm babies (recall: 0,01%). Specificity and sensitivity of the test were nearly 100%. We suggest that screening for biotinidase deficiency should be incorporated into existing neonatal screening programs for inborn errors of metabolism. This suggestion is based on the ease of testing, the necessity for presymptomatic laboratory diagnosis, and on the effectiveness of early treatment of the multiple carboxylase deficiency caused by defective biotinidase.

Amidohydrolases↗

Characteristics of infantile hypothyroidism discovered on neonatal screening.

Clinical and laboratory data from 146 patients with infantile hypothyroidism diagnosed by neonatal screening over a five-year period are presented. In 95 patients there was adequate thyroid imaging or evidence of dyshormonogenesis; of these, 43% had ectopic thyroid tissue, 22% had goitrous hypothyroidism, and 35% had hypoplastic or aplastic glands. Stanford-Binet IQs of the patients at 3, 4, and 5 years of age were identical with those of control subjects. Patients in whom thyroid tissue was demonstrable on radioactive scanning had higher concentrations of T4 and T3, and lower concentrations of TSH and less retarded bone age, but did not differ in ultimate IQ from patients with no demonstrable thyroid tissue. No significant correlation with ultimate IQ was found for any clinical or laboratory factor except for the adequacy of treatment. Eleven children with inadequate treatment had a mean IQ significantly less than that of other patients, 87 +/- 5 (SEM) vs 105 +/- 2. Inadequate treatment was defined essentially by repeated T4 concentrations less than 8 micrograms/dl during treatment. Thus, T4 values in the lower part of the normal range are probably incompatible with maximal intellectual development, and every effort should be exerted to maintain serum T4 levels in the upper half of the normal range during the first year of life.

Child, Preschool↗

Head growth in cystic fibrosis following early diagnosis by neonatal screening.

Growth in length, weight gain, and head circumference were recorded from 3 months to 4 years of age in 25 children with cystic fibrosis diagnosed by neonatal screening. Mean standard deviation (SD) scores at 3 months for length, weight, and head circumference were -0.78, -0.91, and -0.52 respectively. Over the first 2 years length SD scores showed a consistent improvement and stabilised at 0.1 SD below mean from 2 to 4 years. Weight SD scores remained essentially unaltered throughout, approximately 1 SD below the mean. Head circumference, however, after an initial increase from -0.52 at 3 months to -0.25 at 18 months, slowed and fell to 1 SD below the mean at 4 years. The data suggest that head growth continues to lag behind somatic growth in children with cystic fibrosis despite early diagnosis and good nutritional management in early infancy. These data also support functional expression of cystic fibrosis transmembrane conductance regulator in the brain.

Body Height↗

Sweat testing in newborns positive to neonatal screening for cystic fibrosis.

Sweat chloride concentrations above 40 mmol/l are unusual in newborns screened for cystic fibrosis and should be followed up. Centiles of sweat chloride concentrations in newborns positive to cystic fibrosis neonatal screening are presented. There are no significant correlations between age at sweat testing and sweat chloride concentration or quantity of sweat collected.

Aging↗

Coinheritance of alpha-thalassemia-1 and hemoglobin E/beta zero-thalassemia: practical implications for neonatal screening and genetic counseling.

Hemoglobin E (HbE), alpha-thalassemia, and beta-thalassemia are common among Southeast Asians and often occur in compound heterozygous states that complicate neonatal screening. We describe a kindred with alpha-thalassemia-1, HbE, and beta zero-thalassemia. The proband had HbE/beta zero-thalassemia, with severe anemia and failure to thrive. His father also had HbE/beta zero-thalassemia but had coinherited alpha-thalassemia-1 and was free of symptoms.

Adult↗

Cystic fibrosis identified by neonatal screening: incidence, genotype, and early natural history.

The incidence of cystic fibrosis over the last 10 years in East Anglia (a region of the United Kingdom with a population of 2.1 million) has halved. This has happened during the establishment of a neonatal screening programme, which has enabled early diagnosis, genetic counselling, and lately the option of prenatal diagnosis in subsequent pregnancies. One hundred and seven children were born with cystic fibrosis between 1981 and 1990, eight of whom were siblings. The Guthrie blood spots of 82 infants detected by neonatal immunoreactive trypsin screening between 1981 and 1990 were examined for the presence of the most common cystic fibrosis gene mutation (delta F508). It was present in 135 (82%) of the 164 cystic fibrosis genes analysed with 54 (66%) cases being homozygous and 27 (33%) heterozygous. Sixty nine per cent of infants were symptomatic at the time of diagnosis regardless of genotype. No association was found between the early clinical or biochemical features of the disease and homozygosity or heterozygosity for this mutation. Screening for cystic fibrosis using the blood immunoreactive trypsin assay alone remains an effective method of identifying infants with the disease soon after birth, thereby allowing early therapeutic intervention. Genetic counselling and prenatal diagnosis have contributed to a reduction in the number of children born with cystic fibrosis, but may not entirely explain the decreasing incidence of the disease.

Cystic Fibrosis↗

Genetic and clinical features of false-negative infants in a neonatal screening programme for cystic fibrosis.

UNLABELLED: A study was performed on the delayed diagnosis of cystic fibrosis (CF) in infants who had false-negative results in a neonatal screening programme. The genetic and clinical features of false-negative infants in this screening programme were assessed together with the efficiency of the screening procedure in the Lombardia region. In total, 774,687 newborns were screened using a two-step immunoreactive trypsinogen (IRT) (in the years 1990-1992), IRT/IRT + delF508 (1993-1998) or IRT/IRT + polymerase chain reaction (PCR) and oligonucleotide ligation assay (OLA) protocol (1998-1999). Out of 196 CF children born in the 10 y period 15 were false negative on screening (7.6%) and molecular analysis showed a high variability in the genotypes. The cystic fibrosis transmembrane regulator (CFTR) gene mutations identified were delF508, D1152H, R1066C, R334W, G542X, N1303K, F1052V, A120T, 3849 + 10kbC --> T, 2789 + 5G --> A, 5T-12TG and the novel mutation D110E. In three patients no mutation was identified after denaturing gradient gel electrophoresis of the majority of CFTR gene exons. CONCLUSION: The clinical phenotypes of CF children diagnosed by their symptoms at different ages were very mild. None of them presented with a severe lung disease. The majority of them did not seem to have been damaged by the delayed diagnosis. The combination of IRT assay plus genotype analysis (1998-1999) appears to be a more reliable method of detecting CF than IRT measurement alone or combined with only the delF508 mutation.

Child↗

Genotyping of CYP21, linked chromosome 6p markers, and a sex-specific gene in neonatal screening for congenital adrenal hyperplasia.

We investigated the feasibility and diagnostic utility of genotyping 9 CYP21 mutations, linked chromosome 6p markers, and a dimorphic X-Y marker from neonatal screening samples. Blood-impregnated filter papers (Guthrie cards) from 603 randomly chosen New Zealand neonates were genotyped blind to 17-hydroxyprogesterone (17-OHP) levels. Another 50 samples from Swiss and North American infants with correlative hormonal data were also genotyped. DNA was extracted, and gene-specific PCR was performed. CYP21 PCR products were subjected to ligase detection reaction, simultaneously analyzing 9 CYP21 mutations; PCR products of other genes were subjected to direct gel analysis. CYP21 genotyping indicated a heterozygote rate of 2.8% for classic mutations (excluding CYP21 deletions), and 2.0% for nonclassic mutations in New Zealanders. Ten full-term affected neonates showed a wide range of 17-OHP levels (15-1400 nmol/L). Sick or preterm infants or infants screened on the first day of life with high 17-OHP proved genetically unaffected. Genetic linkage disequilibrium was found between two CYP21 mutations and chromosome 6p markers. Guthrie cards can be used to accurately genotype CYP21 and other relevant markers, potentially enhancing the specificity and sensitivity of congenital adrenal hyperplasia screening. CYP21 heterozygote frequency for classic mutations is higher than expected based on genotype compared with that predicted by hormonal newborn screening.

17-alpha-Hydroxyprogesterone↗