Difficulties in selecting an appropriate neonatal thyroid stimulating hormone (TSH) screening threshold.

Area of Science:

• Neonatal screening
• Endocrinology
• Public health

Background:

• The UK Newborn Screening Programme Centre uses a thyroid stimulating hormone (TSH) cut-off of 10 mU/l for congenital hypothyroidism (CHT) detection.
• Regional variations in TSH cut-offs (5-10 mU/l) necessitate examining the impact of threshold adjustments.

Purpose of the Study:

• To evaluate the implications of lowering the TSH screening threshold from 10 mU/l to 6 mU/l for detecting CHT.
• To assess the number of false positives and true positives identified with a reduced TSH threshold.

Main Methods:

• A regional TSH cut-off of 6 mU/l was implemented for infants screened between April 2005 and March 2007.
• Term infants (>35 weeks) with an initial TSH between 6-20 mU/l underwent a second TSH measurement.
• Paediatric endocrinologists reviewed biochemical data for management decisions.

Main Results:

• 148 out of 65,446 infants (0.23%) had an initial TSH >6.0 mU/l.
• 67 term infants (0.1%) had a TSH between 6.1-10.0 mU/l, and 53 had a TSH >10.0 mU/l.
• Four infants with initial TSH 6.1-10.0 mU/l and one with TSH <10 mU/l on second testing were diagnosed with CHT.

Conclusions:

• Reducing the TSH threshold to 6 mU/l increases false positives by 126% but successfully identifies infants requiring treatment for CHT.
• The study suggests that the increased costs associated with a lower threshold are justified by the benefits of early detection.