Progress in laboratory testing of thyroid disease


The standardization of FT4 assays and the harmonization of TSH assays will result in a change in the reference intervals for all FT4 and some TSH tests. In addition both FT4 and TSH results will change after standardization/ harmonization and this will affect the interpretation of cumulative patient results. 

The C-STFT has discussed the standardization/harmonization approach and the impact thereof with the FDA authorities. A dedicated meeting early 2014 confirmed that the scientifically supported approach of the C-STFT was fully acceptable to the FDA and that everything was in place for performing the technical standardization/harmonization. However, the need for performing a benefit risk analysis before implementation emerged.

To this end, the C-STFT is reaching out to stakeholders to seek views on the benefits and risks arising from FT4 standardization and TSH harmonization.

  1. Benefits: We wish to learn about the benefits that you think would be achieved if all fT4 and TSH assays gave comparable results on patient samples.
  2. Risks: We wish to learn about the risks to patient safety and clinical outcomes that you think may arise as a consequence of a change in the numerical results for patients with thyroid disorders who are being followed, despite appropriate adjustments of the reference intervals. Particular attention should be paid to the question of whether standardization for uncomplicated hypo- and hyperthyroidism may detract from assay differences for important clinical populations (nonthyroidal illness, and elderly and pregnant individuals).
  3. Implementation: We wish to hear your views on how clinical laboratories can minimize the identified risks from FT4 standardization and TSH harmonization, and about the role that you could play for the patients you treat.

Please send your comments by e-mail to one of the following three authors of this short paper:

  1. Linda M. Thienpont, PhD, e-mail: linda.thienpont [at]
  2. James D. Faix, MD, e-mail: jfaix [at]
  3. Graham H Beastall, PhD, e-mail: gbeastall [at]

Note this call is being launched in parallel to several journals and to professional organizations for doctors, laboratory specialists and patients.

For the complete papers, the reader is referred to:

  • Thienpont LM, Faix JD, Beastall G. Standardization of Free Thyroxine and Harmonization of Thyrotropin Measurements: A Request for Input from Endocrinologists and Other Physicians. Thyroid 2015;25:1379-80.
  • Clin Endocrinol (Oxf) 2016;84:305-6.
  • Endocr J 2015;62:855-6.
  • Exp Clin Endocrinol Diabetes 2016;124:61-2.
  • Endocrine 2015;50:826-7.
  • Eur Thyroid J 2015;4:217-2.
  • Endocrine Pract 2016;22:374.
  • ThyroWorld Volume 18 Summer 2015; 13-4.