Improved radioassay for human antithyroglobulin

Area of Science:

• Immunology
• Endocrinology
• Radiochemistry

Background:

• Human antithyroglobulin (anti-HTg) antibodies are important biomarkers in autoimmune thyroid diseases.
• Accurate quantification of anti-HTg is crucial for diagnosis and monitoring.
• Existing assays may be affected by interfering substances like serum thyroglobulin (HTg).

Purpose of the Study:

• To develop and validate a radioassay for quantifying human antithyroglobulin (anti-HTg) antibodies.
• To compare the developed assay with existing methods like solid-phase competitive-binding assay (SPCB).
• To investigate the interference of serum thyroglobulin (HTg) on anti-HTg assays.

Main Methods:

• Coprecipitation assay using 125I-labelled human thyroglobulin (HTg).
• Quantification of anti-HTg using a standard serum for calibration.
• Comparison of radioassay results with solid-phase competitive-binding assay (SPCB) and MRC Research Standard A.

Main Results:

• The radioassay demonstrated parallel curves for different sera, enabling reliable quantification.
• Estimated antibody content in standard serum was 0.14 ng anti-HTg per ml.
• The assay showed good correlation with SPCB and MRC Standard A, with established unit conversions.
• Serum HTg interfered with SPCB assay, causing false positives, but minimally impacted the developed radioassay.

Conclusions:

• The developed radioassay provides a robust and accurate method for quantifying human antithyroglobulin antibodies.
• This assay is less susceptible to interference from serum thyroglobulin compared to SPCB assays.
• The findings highlight the importance of considering interfering substances in antibody assays.