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Identifying homozygous sickle cell disease when neonatal screening is not available: a clinic-based observational study.

OBJECTIVES: Life-threatening clinical complications can occur in the first years of life in people with homozygous sickle cell disease. There is consensus that a clinical care programme comanaged by a specialist clinic should follow early-life disease identification. In a setting without widespread neonatal screening for this disease, we predict the percentage of affected births that enrol in specialist clinics during childhood, and the percentage that enrol early enough to benefit from penicillin prophylaxis (which is offered until five years of age). SETTING: A retrospective study of enrolment between 1973 and 1999 at three clinics in Jamaica, the country's only referral centres for sickle cell disease. RESULTS: Among enrolees not screened at birth, observed enrolment by age five was 10.1% (95% confidence interval [CI] 5.7-16.7%) among 1974 births, which is predicted to rise to 35.7% (95% CI 35.0-36.4%) among 1999 births. Observed enrolment by 18 years of age was 45.9% (95% CI 35.7-58.2%) among 1974 births, which is predicted to peak at 61.9% (95% CI 60.5-63.2%) among 1984 births, and fall to 48.9% (95% CI 40.9-56.9%) among 1999 births. Median age at enrolment was 10.5 years (95% CI 10.0-11.3). CONCLUSIONS: Based on 1999 estimates, almost 65% of children affected by homozygous sickle cell disease not identified at birth will not benefit from important early-life clinical intervention, and half will not enrol for specialised care by their 18th birthday. Among patients that enrol, half do so in adolescence when management is less focused on preventive care.

Anemia, Sickle Cell↗

Red blood cell disorders in Rwandese neonates: screening for sickle cell disease and glucose-6-phosphate dehydrogenase deficiency.

OBJECTIVES: To determine the prevalence of haemoglobin (Hb) variants and glucose-6-phosphate dehydrogenase (G6PD) deficiency in Rwanda. METHODS: During a two-month period in 2005, 987 cord blood samples were obtained in two hospitals in Kigali and Butare, Rwanda. Screening for sickle cell disorders, other Hb disorders, G6PD deficiency and other rare erythroenzymopathy deficiencies was done using isoelectric focusing techniques and quantitative kinetic assays, respectively. RESULTS: The prevalence of Hb S trait was 2.7% and that of G6PD deficiency was 3.8%. No neonate suffered from a sickle cell disease (homozygous for Hb S or compound heterozygous for Hb S), from another clinically significant haemoglobinopathy, or from pyruvate kinase or glucose phosphate isomerase deficiency. CONCLUSIONS: Sickle cell disorders should be considered a public health problem in Kigali and Butare. A systematic neonatal screening programme for those disorders, and to diagnose G6PD deficiency, seems reasonable, but local health priorities must be considered. Adapted management of hereditary sickle cell and G6PD disorders should be available.

Anemia, Sickle Cell↗

Extended gene analysis can increase specificity of neonatal screening for cystic fibrosis.

AIM: To assess whether carriers and patients can be accurately identified by extended gene analysis for cystic fibrosis (CF) in dried blood spots. METHODS: A blinded analysis was performed in 10-mm2 blood spots on Guthrie cards, punched as if to remove material for the IRT test, from 10 CF patients and 10 carriers with known CF mutations. Genomic DNA was isolated. Aliquots of 1 microl dissolved DNA were used for subsequent PCRs. Analysis of the deltaF508 mutation was followed by an oligonucleotide ligation assay. Denaturing gradient gel electrophoresis of the whole CFTR gene was carried out in samples with only one identified mutation. Amplicons revealing an aberrant pattern were sequenced. RESULTS: In all cases, the blood-spot genotype was identical to that previously determined from whole-blood analysis. Estimated time needed to complete the procedure in a series of Guthrie cards was 3-4 wk. CONCLUSION: Extended gene analysis in dried blood spots can discriminate CF patients and carriers. If proven equally reliable in larger series, an approach to neonatal screening in which tests are only considered as screen positive when two CF mutations are found is possible. This can increase the specificity of the screening programme, and carrier detection can practically be avoided.

Algorithms↗

[Discovery, in neonatal screening, of 2 families carrying a syndrome of generalized resistance to thyroid hormones].

The syndrome of generalized resistance to thyroid hormones is being increasingly diagnosed, albeit often belatedly. In the two families described herein the diagnosis was established when moderately elevated thyrotropin levels were found upon neonatal screening of a family member. The family studies identified other affected members with a pattern indicating autosomal dominant inheritance. Clinical and laboratory findings in the neonates were consistent with normal thyroid function and no treatment was given. In one neonate, fibroblast nuclear receptor studies failed to detect decreased affinity for triiodothyronine, a finding reported in most previously published cases; the mutation in this patient was different from the one described in 1989 by Sakurai et al., consistent with the known genetic heterogeneity of this syndrome. It has been suggested recently that treatment of affected neonates with large doses of thyroid hormones is safe and effective in ensuring normal growth. The neurodevelopmental effects of this treatment are unknown. Early treatment is possible when the syndrome is detected neonatally. We therefore advocate routine T4 assays in neonates with moderately elevated TSH levels.

Female↗

Potentials and pitfalls in neonatal screening for type 1 diabetes.

Childhood-onset diabetes is increasing all over the western world. Only 20-30% of monozygotic twin pairs are concordant for the disease. So far, more than 20 different risk genes have been identified on different chromosomes. The dominating risk genes differ with different age at onset and also in different populations. Thus, the aetiology of the disease is complex, with interactions between different risk genes and environmental risk factors. Several pathogenetic models have been proposed, most of which include autoimmune destruction mechanisms. Screening for genetic markers for diseases with such complex aetiology encounters pitfalls due to the low predictive value of each single marker in the general population. To overcome such problems combinations of markers and decision-tree analysis are necessary. The identification of several immune markers for the disease has provided potential for screening for secondary prevention. When increasing the number of markers to increase the predictive value, sensitivity will be lost. A Swedish population-based study found the best combined positive predictive value in the general population to be 20%, whereas the sensitivity was only 34%. Type 1 diabetes still needs more precise risk markers in addition to a very safe prevention strategy before neonatal screening programmes may be instituted.

Diabetes Mellitus, Type 1↗

Incidence of congenital toxoplasmosis estimated by neonatal screening: relevance of diagnostic confirmation in asymptomatic newborn infants.

Congenital toxoplasmosis is rarely identified by routine clinical examination. The aim of this study was to estimate the incidence of the disease in the region of Ribeirão Preto, south-eastern Brazil. A definitive diagnosis was made on the basis of the persistence of anti-Toxoplasma IgG antibodies beyond 1 year of age. Blood samples obtained from 15,162 neonates and adsorbed onto filter paper were tested for anti-Toxoplasma IgM antibodies. Fifteen samples gave positive results. A definitive diagnosis was confirmed in five of the 13 infants (38.5%) who completed follow-up. These five infants presented with serum IgM and/or IgA antibodies, and clinical abnormalities. Disease incidence was estimated to be 3.3/10,000 (95% CI 1.0-7.7), indicating the need for preventive measures. Neonatal screening is feasible, but screening tests with a better performance are required; positive screening results must be carefully confirmed.

Animals↗

[One year of neonatal screening for sickle-cell disease in Emma Children's Hospital/Academic Medical Center in Amsterdam].

OBJECTIVE: Early detection of children with sickle cell disease, determination of carriership frequency as well as evaluation of the knowledge regarding this haemoglobinopathy in various ethnic risk groups. DESIGN: Prospective. METHODS: From 1 November 1998 through to 31 October 1999, the ethnic background was recorded for consecutive pregnant women under care of the Academic Medical Centre, Amsterdam, the Netherlands, and the presence of carriership for sickle cell disease was evaluated. Carriers were asked about their knowledge of sickle cell disease. A diagnostic blood test of cord blood was also performed using a PCR which could detect both haemoglobin S and C mutations. RESULTS: Fifty-five carriers were detected in a group of 1,016 investigated pregnant women (5.4%). The carriership frequencies in Surinam and African women were 12 and 15.7%, respectively. Knowledge of sickle cell disease, its occurrence in populations at risk, as well as the terms 'inheritance' and 'carriership', differed substantially between Surinam and African women, with awareness being lower in the latter group. In six cases informed consent was not asked. All other 49 carriers consented to a diagnostic test. Two intrauterine deaths occurred. Four children had sickle cell disease: three had HbSS, one had HbSC. Nineteen children proved to be carriers for sickle cell disease, 18 were heterozygotes for HbS, one for HbC. CONCLUSION: This targeted neonatal screening for sickle cell disease was feasible in a hospital setting. The number of children diagnosed with the disease supports the wider implementation of this method of early detection.

Africa↗

[Automation of T4 and TSH radioimmunoassay in the neonatal screening for hypothyroidism in south-west France (author's transl)].

In the South-West France the neonatal screening service for hypothyroidism using both T4 and TSH undertakes 50 000 assays annually. To obtain maximum reliability and speed the calculations and statistical analysis have been automated. Counting is done by gamma counter linked through magnetic tapes to programmable computer. This provides immediate print-out of hormone levels and for each group of the results the mean and standard deviation of the T4 levels and histogram of the TSH values. The counter also produces a punched paper tape so that the results can be analysed in the detail on a computer (range of values and correlation between T4 and TSH value). The results of the statistical analysis of the T4 and TSH levels are reported.

Autoanalysis↗

The effects of neonatal screening for sickle cell disorders on lifetime treatment costs and early deaths avoided: a modelling approach.

BACKGROUND: The aim of the study was to calculate the cost to the UK National Health Service of providing treatment services for patients with sickle cell disorders. The rates of differential morbidity and mortality, in the first 10 years of life, between screen-detected early diagnosed and clinically presenting late diagnosed cohorts of sickle cell disorder patients are also estimated. METHOD: A cost model was developed, based on predictions of survival and the incidence of sickle cell disorder-related events. Direct data from the NHS are lacking, so data were incorporated from disparate sources. Patients with sickle cell disorders were divided into two categories: those with sickle cell anaemia and those with sickle HbC disease. RESULTS: Differentiating between sickle cell anaemia and sickle HbC disorder patients, the results show that the undiscounted (discounted at 6 per cent) lifetime treatment costs range from pound sterling 92323 (pound sterling 24917) to pound sterling 185614 (pound sterling 53861). The number of early deaths avoided per 100 births, as a result of early diagnosis through screening, ranges from 0.57 to 1.25. CONCLUSIONS: The resulting estimates may act as a guide to those involved in the planning of health care provision with regard to the resources required to treat sickle cell disorder patients. Such information may also be incorporated into the evaluation of both antenatal and neonatal screening programmes for sickle cell disorders.

Adolescent↗

Neonatal screening for maple syrup urine disease by an enzyme-mediated colorimetric method.

A microplate-based, enzyme-mediated, colorimetric method using L-leucine dehydrogenase (EC 1.4.1.9) has been developed for the determination of the combined branched-chain amino acids in plasma and blood-spot specimens. The test exhibits acceptable precision and fits into a new concept according to which the different parameters of neonatal screening programs for metabolic disorders, such as phenylalanine (phenylketonuria), galactose/galactose-1-phosphate (galactosemia) and branched-chain amino acids (maple syrup urine disease) can be measured in the same blood-spot eluate by use of different specific NAD(H)-dependent enzymes.

Amino Acid Oxidoreductases↗

Feasibility of neonatal screening for toxoplasma infection in the absence of prenatal treatment. Danish Congenital Toxoplasmosis Study Group .

BACKGROUND: The best method for prevention and control of congenital toxoplasma infection is uncertain. Prenatal screening is done in Austria and France, but the effect of treatment during pregnancy is not well documented. The aim of our study was to find out the maternofetal transmission rate and outcome in infants born to mothers who were not treated during pregnancy. METHODS: We analysed 89873 eluates from phenylketonuria (PKU) cards from neonates and paired first-trimester serum samples from the mothers for specific IgG antibodies to Toxoplasma gondii. Children born to mothers who seroconverted during pregnancy were followed-up clinically and serologically to 12 months of age. In addition, 21144 PKU cards were analysed for toxoplasma-specific IgM antibodies during the last 12 months of the study. FINDINGS: In 24989 (27.8%) cases both the PKU eluate and the first-trimester samples were IgG positive, which indicates previous maternal infection. 139 of the 64884 seronegative women acquired toxoplasma infection during pregnancy and gave birth to 141 infants (two sets of twins). 27 of these children were diagnosed with congenital toxoplasma infection. The transmission rate was 19.4% (95% CI 13.2-27.0). Clinical signs and symptoms were found in four (15%) of the 27 children. The additional analysis for toxoplasma-specific IgM antibodies from the PKU card identified seven of nine children with congenital toxoplasma infection. The false-positive rate for the IgM test was 0.19 per 1000, and no false-negatives were found. INTERPRETATION: The risks of transmission of infection and of disease in the infant are low in an area with a low risk of toxoplasma infection. A neonatal screening programme based on detection of toxoplasma-specific IgM antibodies alone will identify between 70% and 80% of cases of congenital toxoplasmosis.

Adult↗

Spectrum of CFTR mutations on Réunion Island: impact on neonatal screening.

The large heterogeneity in the cystic fibrosis (CF) gene is the main difficulty for genotype characterization. Numerous studies have reported considerable variations in frequencies of CF transmembrane conductance regulator (CFTR) mutations in different populations, such as African, Asian, or European populations. To completely characterize the spectrum of mutations in the CFTR gene in the Réunion Island population, we screened 228 CF chromosomes using denaturing high-pressure liquid chromatography and denaturing gradient gel electrophoresis following by direct sequencing. We identified 27 mutations, accounting for 93% of CF chromosomes. They included three novel mutations (M1T, 3121-3C-->G, and L1324P), which are described in this paper. The detection of such a high proportion of Réunion Island CFTR mutations is important for improving neonatal screening of CF on Réunion Island.

Cystic Fibrosis↗

[Deterioration of clinical findings in hip joint follow-ups in neonatal screening].

6 per cent out of 4290 hips checked by neonatal ultrasound screening could be reexamined later on. 7 of 200 hips (i.e. 4 per cent), primarily categorized as type IIa, showed an unexpected severe deterioration to type D (n = 3) or even to type IIIa (n = 4) after a mean-time of 9 weeks. Additional 5 cases with similar unfavourable courses from IIa to IIc, D or IIIa, and even 3 initially normal hips, changing to type IIa, were seen in another screening material (not yet systematically analyzed). Reasons for possible initial misinterpretation (purely visual evaluation in most cases, uncertainties in measuring suboptimal sonographic cuts, deficiencies in technical equipment and documentation), equivocal classification of border-line sonograms as well as possible influence of additional risk factors are discussed. Routine sonographic re-examinations after 6 (to 12) weeks are recommended as obligatory for all hips.

Diagnosis, Differential↗

Costing model for neonatal screening and diagnosis of haemoglobinopathies.

AIM: To compare the costs and cost effectiveness of universal and targeted screening for the haemoglobinopathies; to compare the cost of two laboratory methods; and to estimate the cost effectiveness of programmes at different levels of prevalence and mix of haemoglobinopathy traits. METHODS: A retrospective review of laboratory and follow up records to establish workload and costs, and estimation of costs in a range of circumstances was made in a haematology department and sickle cell and thalassaemia centre, providing antenatal and neonatal screening programmes in Inner London. The costs for 47,948 babies, screened during 1994, of whom 25 had clinically significant haemoglobinopathies and 704 had haemoglobinopathy traits, were retrospectively assessed. RESULTS: The average cost per baby tested (isoelectric focusing and high power liquid chromatography) was 3.51 Pounds /3.83 Pounds respectively; the cost per case of sickle cell disease identified (IEF/HPLC) was 6738 Pounds /7355 Pounds; the cost per trait identified (IEF/HPLC) was 234 Pounds /255 Pounds; the cost per extra case of SCD and trait identified by universal programme varied. CONCLUSIONS: IEF and HPLC are very similar in terms of average cost per test. At 16 traits/1000 and 0.5 SCD/1000 there was no significant identification cost difference between universal and targeted programmes. Below this prevalence, a targeted programme is cheaper but likely to miss cases of SCD. If targeted programmes were 90-99% effective, universal programmes would cease to be good value except at very high prevalence. Greater use of prenatal diagnosis, resulting in termination, and therefore fewer affected births, reduces the cost effectiveness of universal screening. Screening services should aim to cover a screened population which will generate a workload over 25,000 births a year, and preferably over 40,000.

Chromatography, High Pressure Liquid↗

[Prevalence of frequent recessive diseases in the Spanish population through DNA analyses on samples from the neonatal screening].

BACKGROUND AND OBJECTIVE: Cystic fibrosis (CF) and the nonclassical forms of congenital adrenal hyperplasia (NC21OHD) are frequent autosomal recessive diseases. Their frequencies in the Caucasian population are the ones applied to the management of the diseases (1:2500 and 1:1000, respectively). The aim of this study was to learn about the adequacy of these figures to the Spanish population. MATERIAL AND METHOD: Study of the recurrent mutation (about 50% of alleles) in each entity, DF508 or Val281Leu, respectively, in 300 anonymous consecutive samples (600 alleles) from the Comunidad de Madrid neonatal screening. PCR specific amplifications of the CFTR and CYP21A2 genes and direct analyses of DF508 and Val281Leu mutations were performed. RESULTS: Allele frequencies of DF508 and Val281Leu were 0.005 and 0.038 (carrier frequencies 1.1% and 7.5%, respectively). Taking into consideration the percentage of these mutations in patient alleles, 48% for CF and for 57% NC21OHD, disease frequencies of about 1:8028 (CF) and 1:230 (NC21OHD) were estimated. The standard error calculated for these data were 0.6% and 1.5%. CONCLUSIONS: We have found that CF is less frequent and NC21OHD more frequent in the Spanish population than in other Caucasian populations.

Adrenal Hyperplasia, Congenital↗

Longitudinal assessment of children with congenital hypothyroidism detected by neonatal screening.

Clinical and laboratory data from 42 children (31 females and 11 males) with primary congenital hypothyroidism (CH) diagnosed by neonatal screening over a six-year period are reported. The mean age at onset of thyroid hormone therapy was 33 days. The adequacy of replacement therapy was assessed by repeated TT4, FT4, T3 and TSH serum determinations. The high serum TT4 concentrations frequently observed were not accompanied by clinical evidence of hyperthyroidism. rT3 levels determined in 28 CH children with TT4 greater than 15 micrograms/dl were clearly higher than in the controls. The mean weight, length and head circumference remained always between the 50th and 75th centile. The radiological assessment of the knee, mainly the distal femoral surface, has been considered as an important clinical value in the initial diagnosis and in the evaluation of both severity and duration of disease. The psychomotor development was assessed using Brunet-Lezine's test until age 36 months, Stanford-Binet at 4 and 5 and WISC at 6 years of age. The mean global developmental quotients (GDQ) were always between 85 and 97 at 6 to 72 months of age, only eight children were below 85. A significant correlation was found between GDQ at 6 months and the bone age. The neurological examination showed an impairment of posture, coordination and subtle deficits in motor and perceptual abilities in a small percentage of children.

Age Determination by Skeleton↗

Severe hemolytic anemia associated with vitamin E deficiency in infants with cystic fibrosis. Implications for neonatal screening.

Three infants are described with cystic fibrosis (CF) and malnutrition leading to severe anemia beginning as early as 6 weeks of age. Laboratory studies demonstrated high reticulocyte counts, negative Coombs' tests, abnormal peroxide hemolysis test results, and biochemical evidence of vitamin E deficiency. Oral administration of alpha-tocopherol resulted in rapid correction of the in vitro hemolysis and improvement of in vivo hematologic indices. Investigation of these patients supports the conclusion that the hemolytic anemia of infancy in CF is caused by vitamin E deficiency and should be treated promptly with 50 IU/day of vitamin E. Because two of the three patients were identified in a CF screening/surveillance program, we can estimate that the frequency of clinically significant anemia in CF infants is 4%. Our observations demonstrate a potential advantage of CF neonatal screening for individual patients susceptible to vitamin E-deficient hemolytic anemia and suggest that confirmatory follow-up diagnostic studies, such as sweat tests, should be performed by 4 to 6 weeks of age.

Anemia, Hemolytic↗

Efficacy of statewide neonatal screening for cystic fibrosis by assay of trypsinogen concentrations.

BACKGROUND: To evaluate the feasibility and efficacy of measuring immunoreactive trypsinogen in blood to screen for cystic fibrosis, we performed this test in 279,399 newborns in Colorado from 1982 to 1987. METHODS: Immunoreactive trypsinogen was measured in dried blood spots when the infants were 1 to 4 days old; if the level was elevated (greater than or equal to 140 micrograms per liter), the measurement was repeated (mean age, 38 days); if the level was again elevated, sweat testing was performed (mean age, 49 days). For the second test, two cutoff levels (120 and 80 micrograms per liter) were evaluated. RESULTS: We found an incidence of cystic fibrosis of 1 in 3827 (0.26 per 1000), with 3.2 newborns per 1000 requiring repeat measurement. When adjusted for race and compliance with testing, the incidence among the white infants (1 in 2521) was close to the expected incidence. The false positive rate with the initial cutoff level (92.2 percent) was similar to the rate found in neonatal screening programs for other diseases. False negative results occurred because of laboratory error or changes in procedure (three infants) and trypsinogen concentrations lower than the initial cutoff level (three infants) or lower than the remeasurement cutoff level of 120 micrograms per liter (one infant). Sweat tests were negative in 168 infants with an elevated initial trypsinogen level but a level below 80 micrograms per liter on remeasurement, confirming the value of 80 micrograms per liter as an appropriate cutoff for repeat-test results. Overall, 95.2 percent of the infants with cystic fibrosis (95 percent confidence interval, 85 to 99 percent) who did not have meconium ileus could be identified with the use of a trypsinogen cutoff level of 140 micrograms per liter on initial testing and 80 micrograms per liter on repeat testing. CONCLUSIONS: Statewide screening for cystic fibrosis based on measurements of immunoreactive trypsinogen in dried blood spots is feasible and can be implemented with acceptable rates of repeat testing and false positive and false negative results.

Clinical Protocols↗