Fifty years of newborn screening for congenital hypothyroidism: current status in Australasia and the case for harmonisation

Abstract

Objectives: Since its implementation 50 years ago in Quebec, Canada, newborn screening for congenital hypothyroidism has become one of the most successful public health measures worldwide. Screening programmes across Australia and New Zealand are characterised by significant commonalities in screening algorithms, and a high degree of regional cooperation in harmonisation efforts. We aimed to conduct a comprehensive survey of current performance and practices related to the total testing process for congenital hypothyroidism screening and provide recommendations for harmonisation priorities within our region.

Methods: A survey was conducted involving the six newborn screening laboratories which provide complete geographic coverage across Australasia. Approximately 360,000 newborns are screened annually. Survey questions incorporated pre-analytical, analytical, and post-analytical aspects of the screening programmes and an extensive 5-year (2016-2020) retrospective analysis of individual programme performance data. Responses from individual screening programmes were collated.

Results: The uptake of newborn screening was over 98% for the six major jurisdictions. All programmes have adopted a single-tier thyroid stimulating hormone (TSH) strategy using the Perkin Elmer GSP instrument. Significant similarities exist between programmes for recommended age of collection and recollection protocols for low birthweight newborns. The process for the determination of TSH cutoffs varies between programmes. TSH lower cut-offs for borderline-positive and positive notifications between 12-15 and 12-25 mIU/L blood, respectively. Recall rates vary between 0.08 and 0.20%. The case definition for congenital hypothyroidism generally includes biochemical and radiological parameters in addition to the commencement of thyroxine. All programmes reported collecting biochemical and clinical data on infants with positive screening tests, and positive predictive values vary between 23.6 and 77.3%. Variation in reported incidence (1:1,300-2,000) cannot be entirely explained by cutoff or recall rate (although one programme reporting fewer cases includes only permanent disease).

Conclusions: Despite similarities between newborn screening algorithms for congenital hypothyroidism across Australia and New Zealand, differences in reported programme performance provide the basis for further harmonisation. Surveillance of a large population offers the potential for the ongoing development of evidence-based screening guidelines.

Keywords: congenital hypothyroidism; harmonisation; newborn screening.