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Difficulties in selecting an appropriate neonatal thyroid stimulating hormone (TSH) screening threshold
  1. Srinivasa Murthy Korada1,
  2. Mark Pearce1,
  3. Martin P Ward Platt2,
  4. Enid Avis3,
  5. Steve Turner4,
  6. Hilary Wastell4,
  7. Tim Cheetham5
  1. 1Institute of Health and Society, Newcastle University, Sir James Spence Institute, Royal Victoria Infirmary, Newcastle upon Tyne, UK
  2. 2Neonatal Service, Royal Victoria Infirmary, Newcastle upon Tyne, UK
  3. 3Department of Paediatrics, Royal Victoria Infirmary, Newcastle upon Tyne, UK
  4. 4Department of Clinical Biochemistry, Royal Victoria Infirmary, Newcastle upon Tyne, UK
  5. 5Institute of Human Genetics, Newcastle University, Department of Paediatrics, Royal Victoria Infirmary, Newcastle upon Tyne, UK
  1. Correspondence to Dr Tim Cheetham, Institute of Human Genetics, Newcastle University, Department of Paediatrics, Royal Victoria Infirmary, Newcastle upon Tyne NE1 4LP, UK; tim.cheetham{at}nuth.nhs.uk

Abstract

Background The UK Newborn Screening Programme Centre recommends that a blood spot thyroid stimulating hormone (TSH) cut-off of 10 mU/l is used to detect congenital hypothyroidism (CHT). As the value used varies from 5 to 10 mU/l, we examined the implications of altering this threshold.

Methods Our regional blood spot TSH cut-off is 6 mU/l. Positive or suspected cases were defined as a TSH >6 mU/l throughout the study period (1 April 2005 to 1 March 2007). All term infants (>35 weeks) whose first TSH was 6–20 mU/l had a second TSH measured. The biochemical details of infants with a TSH between 6.1 and 10.0 mU/l and then >6 mU/l on second sampling were sent to paediatric endocrinologists to determine approaches to management.

Results 148 of 65 446 infants (0.23%) had a first blood spot TSH >6.0 mU/l. 120 were term infants with 67 of these (0.1% of all infants tested) having a TSH between 6.1 and 10.0 mU/l and 53 a TSH >10.0 mU/l. Of the 67 term infants with a TSH between 6.1 and 10.0 mU/l on initial testing, four continued to have a TSH >6 mU/l. One with a TSH >10 mU/l and one infant with a TSH <10 mU/l on the second blood spot have been diagnosed with CHT. The survey of endocrinologists highlighted significant differences in practice.

Conclusions A reduced threshold of 6 mU/l will increase the number of false positive term infants by 126%, but abnormalities of thyroid function requiring treatment will be detected. We suspect that the additional expense involved in setting a lower threshold is justified.

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Footnotes

  • Competing interests None.

  • Ethics approval This study was conducted with the approval of the Newcastle and North Tyneside Research Ethics Committee.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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