Newborn Screening for Primary Congenital Hypothyroidism: Estimating Test Performance at Different TSH Thresholds.

Context: Active surveillance of primary congenital hypothyroidism (CH) in a multiethnic population with established newborn bloodspot screening. Objective: To estimate performance of newborn screening for CH at different test thresholds and calculate incidence of primary CH. Design: Prospective surveillance from June 2011 to June 2012 with 3-year follow-up of outcomes. Relative likelihood ratios (rLRs) estimated to compare bloodspot TSH test thresholds of 6 mU/L and 8 mU/L, with the nationally recommended standard of 10 mU/L for a presumptive positive result. Setting: UK National Health Service. Patients: Clinician notification of children aged <5 years investigated following clinical presentation or presumptive positive screening result. Main Outcome Measure(s): Permanent primary CH status determined by clinician report of continuing T4 requirement at 3-year follow-up. Results: A total of 629 newborns (58.3% girls; 58.7% white ethnicity) were investigated following presumptive positive screening result and 21 children (52.4% girls; 52.4% white) after clinical presentation; 432 remained on treatment at 3-year follow-up. Permanent CH incidence was 5.3 (95% CI, 4.8 to 5.8) per 10,000 infants. With use of locally applied thresholds, sensitivity, specificity, and positive predictive value were 96.76%, 99.97%, and 66.88%, respectively. Compared with a TSH threshold of 10 mU/L, positive rLRs for 8 mU/L and 6 mU/L were 1.20 (95% CI, 0.82 to 1.75) and 0.52 (95% CI, 0.38 to 0.72), and negative rLRs were 0.11 (95% CI, 0.03 to 0.36) and 0.11 (95% CI, 0.06 to 0.20), respectively. Conclusions: Screening program performance is good, but a TSH threshold of 8 mU/L appears superior to the current national standard (10 mU/L) and requires further evaluation. Further research should explore the implications of transient CH for screening policy.

Synthesis framework estimating prevalence of MCADD and sensitivity of newborn screening programme in the absence of direct evidence.

BACKGROUND AND OBJECTIVES: Several countries have included medium-chain acyl-CoA dehydrogenase deficiency (MCADD) in their newborn screening programs. However, the sensitivity of the programs cannot be estimated directly as only individuals with a positive result undergo a definitive diagnostic test. We propose a framework to overcome this limitation and estimate the prevalence of disease, sensitivity of screening, and its yield relative to no screening. STUDY DESIGN AND SETTING: A Bayesian model simultaneously combined available prevalence data on the most common mutation of MCADD (c.985A>G) in screened and nonscreened populations using the relationship between true and apparent prevalence of disease. Data originated from screening pilots in England, disease surveillance studies, and published literature. Model validity and consistency were formally checked. RESULTS: True prevalence of c.985A>G homozygotes in England was 6.2 per 100,000 individuals, and the sensitivity of the screening program was 94% (95% confidence interval [CI]: 74, 100%) compared with a detection rate in nonscreened areas of 48% (95% CI: 30, 68%) by age of 5 years. Hence, the screening program detected 47% (95% CI: 30, 60%) additional cases compared with no screening. CONCLUSION: The sensitivity of the screening program in England was high and our estimation approach could be adapted to inform other jurisdictions, rare diseases, and newborn screening programs.

Late clinical presentation of congenital adrenal hyperplasia in older children: findings from national paediatric surveillance.

OBJECTIVES: To describe the clinical presentation and sequelae, including salt-wasting crises of newly-diagnosed congenital adrenal hyperplasia (CAH) in children aged over 1 year in a contemporary population without screening. To appraise the potential benefit of newborn screening for late-presenting CAH. DESIGN: Active national surveillance undertaken in Great Britain prospectively from 2007-2009 through the British Paediatric Surveillance Unit. SETTING: England, Wales and Scotland. PATIENTS: Children first presenting aged 1-15 years with clinical features of CAH and elevated 17-hydroxyprogesterone. RESULTS: Fifty-eight children (26 [45%] boys) aged 1-15 years were reported; 50 (86%) had 21-hydroxylase deficiency. Diagnosis was precipitated by secondary sexual characteristics (n=38 [66%]; median age 5.8 [IQR] 4.8, 7.6) years, genital virilisation (8 girls; 3.2 [IQR 1.3, 7.3] years) or an affected sibling (n=8; 10.0 [IQR 7.4, 13.3] years). At least 33 (57%) children had advanced bone age and 13 (30%) were obese (body mass index ≥ 95 th centile). No child had experienced a salt-wasting crisis. CONCLUSIONS: In Great Britain, 30 children aged 1-15 years present annually for the first time with CAH. Older children frequently manifest prematurely advanced epiphyseal and pubertal maturation and genital virilisation, which are often irreversible and likely to have long-lasting consequences for adult health and wellbeing. Almost one-third of affected children are obese before commencing steroid therapy. Newborn screening offers the potential to avoid serious clinical manifestations in older children with unrecognised CAH; however, it may also detect some children who would otherwise remain asymptomatic and for whom the benefit from treatment is uncertain.

Incidence and clinical features of congenital adrenal hyperplasia in Great Britain.

OBJECTIVES: To estimate the incidence of clinically diagnosed congenital adrenal hyperplasia (CAH), clinical features and age at first presentation. To assess the potential benefit of newborn screening for CAH. DESIGN: Active surveillance through the British Paediatric Surveillance Unit of all children aged under 16 years with newly diagnosed CAH, undertaken prospectively between August 2007 and August 2009. Twelve laboratories testing for CAH reported new diagnoses between August 2007 and January 2009. Reporting clinicians completed clinical questionnaires. SETTING: England, Wales and Scotland. RESULTS: 144 children with CAH were reported, of whom 132 (92%) had 21-hydroxylase deficiency. Thirty-six (25%) children were Asian and 62 (43%; 95% CI 35% to 51%) were boys. Incidence of new diagnoses in children ≤ 16 years was 0.60 (95% CI 0.50 to 0.71) per 100,000. Eighty-six (59%; 36 boys) children were diagnosed in the first year of life (estimated birth prevalence 5.48 (95% CI 4.42 to 6.81) per 100,000), most (77; 89%) of whom presented in the first month of life. Virilised genitalia were found in three-quarters of girls. Twenty-seven newborns first presented with salt-wasting crises, of whom 18 (67%; 16 boys) presented on or after 14 days of age. CONCLUSIONS: Approximately one child in every 18 000 born in Great Britain has CAH. Similar numbers of boys and girls present clinically in the first year of life, but boys present with more severe manifestations, such as salt-wasting crises. Around 70% of newborns who first present with salt-wasting crisis would be detected earlier through newborn screening.

Newborn screening for medium chain acyl-CoA dehydrogenase deficiency in England: prevalence, predictive value and test validity based on 1.5 million screened babies.

BACKGROUND: Medium chain acyl-CoA dehydrogenase deficiency (MCADD) is a rare, life-threatening condition. Early diagnosis by screening asymptomatic newborns may improve outcome, but the benefit to newborns identified with variants not encountered clinically is uncertain. OBJECTIVE: To estimate, overall and by ethnic group: screen-positive prevalence and predictive value (PPV); MCADD prevalence; proportion MCADD variants detected of predicted definite or uncertain clinical importance. SETTING: All births in areas of high ethnic minority prevalence in England. METHODS: Prospective multicentre pilot screening service; testing at age five to eight days; standardized screening, diagnostic and management protocols; independent expert review of screen-positive cases to assign MCADD diagnosis and predicted clinical importance (definite or uncertain). RESULTS: Approximately 1.5 million babies (79% white; 10% Asian) were screened. MCADD was confirmed in 147 of 190 babies with a positive screening result (screen-positive prevalence: 1.20 per 10,000; MCADD prevalence: 0.94 per 10,000; PPV 77% [95% CI 71-83]), comprising 103 (70%) with MCADD variants of definite clinical importance (95 white [95%]; 2 Asian [2%]) and 44 (30%) with variants of uncertain clinical importance (29 white [67%]; 12 Asian [28%]). CONCLUSION: One baby in every 10,000 born in England is diagnosed with MCADD by newborn screening; around 60 babies each year. While the majority of MCADD variants detected are predicted to be of definite clinical importance, this varies according to ethnic group, with variants of uncertain importance most commonly found in Asian babies. These findings provide support for MCADD screening but highlight the need to take account of the ethnic diversity of the population tested at implementation.

Relationship of octanoylcarnitine concentrations to age at sampling in unaffected newborns screened for medium-chain acyl-CoA dehydrogenase deficiency.

BACKGROUND: Although octanoylcarnitine (C8) concentrations measured from newborn screening dried blood spots are used to identify those at high risk of medium-chain acyl-CoA dehydrogenase deficiency (MCADD), age-related reference values are currently not available for unaffected newborn populations. Because age at sampling may vary within and between screening programs, variations in C8 concentrations by age may affect screening program performance. We determined whether C8 concentrations vary by age at sampling, sex, birth weight, or gestational age in unaffected newborns. METHODS: We analyzed C8 concentrations from 227,098 unaffected newborns, including 179,729 from 6 English laboratories participating in a multicenter study and 47,369 from the single laboratory serving the New South Wales (NSW) Newborn Screening Program in Australia. In England, the majority of samples were collected at age 5-8 days and analyzed underivatized by use of tandem mass spectrometry (MS/MS); in NSW, samples were obtained at a median age of 3 days and analyzed derivatized by MS/MS. Information on infants' sex, birth weight, gestation, hospitalization, and transfusion status was recorded at time of sampling. RESULTS: C8 concentrations did not vary significantly by age at sampling, sex, birth weight, or gestational age and remained relatively constant during the first 2 weeks of life in unaffected babies being screened for MCADD. CONCLUSIONS: Newborn MCADD screening programs using this biomarker for screening samples collected after the first day and during the first 14 days of life do not need to adjust cutoff values to account for postnatal age, prematurity, or size at birth.