Time-resolved immunofluorometric assay for thyrotropin improved for enhanced functional sensitivity and clinical discrimination

Abstract

Taimela E, Koskinen P, Irjala K. Time-resolved immunofluorometric assay for thyrotropin improved for enhanced functional sensitivity and clinical discrimination. Scand J Clin Lab Invest 1994; 54: 317-21.

Modification of a new commercial time-resolved immunofluorometric assay for thyrotropin (Delfia^R hTSH Ultra) by prediluting samples, reducing tracer concentration, and increasing total reaction volume offered improved functional sensitivity of 0.005 mlUl⁻¹ (20% between-assay CV) over the functional sensitivity limit of.0.014mIUr⁻¹ of the unmodified TSH assay.

Serum TSH concentrations of 50 hyperthyroid patients and 24 clinically euthyroid patients with serum TSH<0.1mIUr⁻¹ by a second generation immunoradiometric assay were analysed by both the original and modified TSH-IFMA method. The discrimination was better with the modified method, according to ROC-analysis (p = 0.027).

In conclusion, these modifications enhanced functional sensitivity and improved the discriminatory power of the assay in separating hyperthyroid patients from euthyroid subjects with low TSH concentrations.

Key Words:

• third-generation TSH assay
• thyroid function