Enzyme immunoassay of thyroxin-binding globulin

Area of Science:

• Biochemistry
• Immunology
• Endocrinology

Background:

• Thyroxin-binding globulin (TBG) is essential for thyroid hormone transport.
• Accurate TBG measurement is vital for diagnosing thyroid disorders and managing hormone replacement therapy.

Purpose of the Study:

• To develop and validate a novel double-antibody enzyme immunoassay for serum TBG.
• To assess the assay's analytical performance, including recovery, linearity, and precision.

Main Methods:

• A TBG-beta-D-galactosidase conjugate was synthesized using m-maleimidobenzoyl N-hydroxysuccinimide ester.
• A double-antibody enzyme immunoassay format was employed for serum TBG quantification.
• Assay validation included recovery, linearity, precision (within- and between-assay), and correlation with radioimmunoassay.

Main Results:

• The assay demonstrated excellent analytical recovery (mean 99%) and linearity with sample volume.
• High correlation (r = 0.98) was observed between the new method and established radioimmunoassay.
• Coefficients of variation averaged 7.6% (within-assay) and 6.6% (between-assay), indicating good precision.
• The measurable range was 3.3 to 52 mg/L, extendable for higher concentrations.

Conclusions:

• The developed enzyme immunoassay provides a reliable and precise method for serum TBG determination.
• This assay is suitable for routine clinical use, aiding in the diagnosis of TBG-related disorders.
• The method offers an alternative to radioimmunoassay for quantifying TBG levels.