Global FT4 immunoassay standardization: an expert opinion review

Area of Science:

• Clinical Chemistry
• Laboratory Medicine
• Endocrinology

Background:

• Free thyroxine (FT4) assay results vary significantly between different measurement methods.
• This variability hinders the comparability of results across laboratories and the development of evidence-based clinical guidelines.

Purpose of the Study:

• To outline the process and challenges in standardizing free thyroxine (FT4) assays.
• To emphasize the need for global standardization to improve diagnostic accuracy and patient care.

Main Methods:

• Review of the International Federation of Clinical Chemistry and Laboratory Medicine Committee for Standardization of Thyroid Function Tests' initiatives.
• Discussion of FT4 immunoassay method comparison, recalibration studies, and reference measurement procedure development.

Main Results:

• Substantial progress has been made towards FT4 assay standardization.
• Technical and logistical challenges persist, requiring further studies for common reference intervals and clinical decision limits.

Conclusions:

• Global standardization of FT4 assays is achievable through collaborative efforts among manufacturers, laboratories, and clinicians.
• A comprehensive education program is essential to manage the transition and clinical impact of standardized FT4 testing.