Evaluation of the revised New Zealand national newborn screening protocol for congenital hypothyroidism.

OBJECTIVE: The aim of this study was to assess the performance of the revised New Zealand (NZ) newborn screening TSH cut-offs for congenital hypothyroidism (CHT). METHODS: Screening data over 24 months were obtained from the NZ newborn metabolic screening programme, which utilizes a 2-tier system of direct clinical referral for infants with markedly elevated TSH, and second samples from those with mild TSH elevation. We evaluated the impact of a reduced TSH threshold (50 to 30 mIU/l blood) for direct notification and a lower cut-off (15 to 8 mIU/l blood) applied to second samples and babies older than 14 days. RESULTS: In 2013 and 2014, 117 528 infants underwent newborn screening for CHT. Fifty-two CHT cases were identified by screening (47 general newborn population, five repeat testing in low-birth-weight infants) and one case was missed. Thirty-two infants with screening TSH ≥30 mIU/l were directly referred at a median of 9 days (5-14) and 15 with TSH 15-29 mIU/l were referred after a second sample at a median of 20 days (9-52, P < 0·001). All directly referred infants were confirmed as CHT cases with no earlier referrals as a result of the reduced threshold. The lower TSH cut-off applied to second samples lead to the identification of six extra cases of CHT (15% increase) from seven extra clinical referrals. CONCLUSIONS: The NZ screening programme achieved a 15% increase in CHT case detection for minimal increase in workload or anxiety for families of healthy infants. A further decrease in the threshold for direct referral may allow earlier diagnoses.

Newborn screening for congenital adrenal hyperplasia in New Zealand, 1994-2013.

OBJECTIVE: The objective of the study was to evaluate the efficacy of national newborn screening for severe congenital adrenal hyperplasia (CAH) in New Zealand over the past 20 years. METHODS: Newborn screening for CAH is performed through the estimation of 17-hydroxyprogesterone by a Delfia immunoassay. CAH cases diagnosed in the newborn period from 1994 to 2013 were identified from Newborn Metabolic Screening Programme records. RESULTS: Between 1994 and 2013, 44 neonates (28 females, 16 males) were diagnosed with CAH, giving an incidence of 1:26 727. Almost half (n = 21) of the newborns with CAH were detected solely via screening (not clinically suspected), including 21% of all affected females. Among the group solely ascertained by screening, 17-hydroxyprogesterone sampling occurred at a mean age of 3.3 days (range 2-8 d), the duration from sampling to notification was 5.2 days (0-12 d), and treatment was initiated at 12.0 days (6-122 d). Vomiting was present in 14% of those ascertained by screening, but none had hypotension or collapse at diagnosis. Increasing age at treatment was correlated with a progressive decrease in serum sodium (r = -0.56; P < .0001) and an increase in serum potassium concentrations (r = 0.38; P = .017). Compared with newborns diagnosed by screening alone, those clinically diagnosed were predominantly female (96% vs 29%; P < .0001), notification occurred earlier (4.8 vs 8.5 d; P = .002), and had higher serum sodium (136.8 vs 130.8 mmol/L; P < .0001) and lower serum potassium (5.3 vs 6.0 mmol/L; P = .011) concentrations. CONCLUSIONS: Screening alone accounted for nearly 50% cases of CAH detected in the newborn period, including a fifth of affected females, indicating that clinical diagnosis is unreliable in both genders. Symptoms were mild at diagnosis and there were no adrenal crises. This study confirms the benefits of newborn CAH screening.

Etiology of increasing incidence of congenital hypothyroidism in New Zealand from 1993-2010.

BACKGROUND: Recent reports suggest that the incidence of congenital hypothyroidism (CHT) is increasing in some countries. The etiology of this change is unclear, and it may relate to changes in screening thresholds. We aimed to determine whether the incidence of CHT in New Zealand has changed and whether ethnic-specific rates and the rates of CHT subtypes have also changed. METHODS: The New Zealand neonatal TSH-based screening program has prospectively identified cases of CHT using the same assay and screening thresholds since 1993. Thyroid scintiscans are routinely recommended. We retrospectively identified all cases of CHT requiring levothyroxine treatment from 1993-2010 recorded by the national newborn screening program (>99.5% coverage). Among other parameters, ethnic and CHT subtype-specific incidence rates were calculated. RESULTS: There were 330 new cases of CHT and 1,053,457 live births registered in New Zealand in the 18-yr period, and 86% of cases had a scintiscan, 67% of which had thyroid dysgenesis (female to male ratio 5.0:1.0) and 33% dyshormonogenesis (0.9:1.0). The overall incidence of CHT rose from 2.6 to 3.6 per 10,000 live births (P < 0.01). The incidence of dyshormonogenesis (P = 0.01) increased but not of dysgenesis (P = 0.13). This was mediated by a 2-fold increase in Asian births and 40% increase in Pacific Island births. Both ethnic groups displayed higher rates of dyshormonogenesis compared with New Zealand Europeans (odds ratio 3.3 and 2.6, respectively). There was no change in the ethnic-specific incidences of CHT. CONCLUSION: Although the incidence of congenital hypothyroidism in New Zealand has increased, this is due to changes in the country's ethnic composition.