Utility of third generation thyrotropin assays in thyroid function testing

Area of Science:

• Clinical Chemistry
• Endocrinology
• Immunoassay Technology

Background:

• Thyrotropin (TSH) testing is the primary method for assessing thyroid function.
• Third-generation TSH assays provide enhanced sensitivity, with functional sensitivity down to 0.01-0.02 mU/l.
• Evaluating assay precision and functional sensitivity is crucial for reliable thyroid testing.

Purpose of the Study:

• To analyze the interassay precision of a third-generation TSH assay (ACS:180 TSH-3).
• To assess the role of time span in determining functional sensitivity.
• To compare results from two different third-generation TSH assays and evaluate their clinical utility.

Main Methods:

• Interassay precision profiles of the ACS:180 TSH-3 assay were analyzed.
• Functional sensitivity was determined using five serum pools across 30 runs over 6 weeks.
• TSH concentrations were measured using ACS:180 TSH-3 and Elecsys TSH assays in healthy donors and various patient populations.

Main Results:

• Functional sensitivity of the ACS:180 TSH-3 assay was determined to be 0.015 mU/l.
• High correlation (r=0.76) was observed between ACS:180 TSH-3 and Elecsys TSH assays, though discordant results occurred in some samples.
• Euthyroid reference intervals were established: 0.30-3.68 mU/l (ACS:180 TSH-3) and 0.36-3.64 mU/l (Elecsys TSH).

Conclusions:

• Third-generation TSH assays are valuable for specific clinical situations, including functional thyroid autonomy, monitoring T4 therapy post-thyroidectomy, and assessing TSH in severe nonthyroidal illnesses.
• These assays enable accurate diagnosis and monitoring without additional tests in certain scenarios.
• The use of third-generation TSH assays is recommended for specialized clinical laboratories.