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. In the short paper referred below, we seek the views of patient based Thyroid Foundations in three areas:

  1. Benefits: We wish to learn of the benefits that you think would be achieved if all FT4 assays and all TSH assays give comparable results on patient samples.
  2. Risks: We wish to learn of the risks to patient safety and clinical outcomes that you think may arise as a consequence of a change in reference intervals and cumulative results for patient samples.
  3. Implementation: We wish to hear your views on the roles that should be played by the manufacturers of FT4 and TSH assays, clinical laboratories, doctors treating patients with thyroid disorders, and Thyroid Foundations in minimizing the identified risks from FT4 standardization and TSH harmonization.


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

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]

For the complete paper, the reader is referred to: Inquiry: Standardization of Thyroid Tests The future standardization of FT4 and harmonization of TSH measurements in serum. A request for input on benefits and risks from Thyroid Foundations. ThyroWorld  Volume 18 Summer 2015; 13-4.