A new solid phase immunoradiometric assay for antithyroid microsomal antibody.

Area of Science:

• Immunology
• Endocrinology
• Assay Development

Background:

• Antithyroid microsomal (anti-M) antibodies are key biomarkers in autoimmune thyroid diseases.
• Existing assays for anti-M antibodies have limitations in sensitivity and quantification.

Purpose of the Study:

• To develop and validate a new, sensitive, quantitative, and specific immunoradiometric assay (IRMA) for detecting anti-M antibodies.
• To compare the performance of the developed IRMA with existing methods like passive hemagglutination.

Main Methods:

• Development of an immunoradiometric assay (IRMA) using microtiter plates coated with thyroid microsomal antigen.
• Detection of anti-M antibody using purified [125I]antihuman immunoglobulin G (IgG).
• Testing of patient serum samples and normal controls, with comparison to passive hemagglutination results.

Main Results:

• The IRMA detected anti-M antibodies in all patients with Hashimoto's thyroiditis or idiopathic myxedema (100%) and 86% of Graves' disease patients.
• The assay showed good correlation with passive hemagglutination but detected antibodies in some cases with negative hemagglutination tests.
• Quantitative measurements revealed a sensitivity 15-30 times greater than competitive binding radioassays, with a minimal detectable amount of 1-2 ng IgG.

Conclusions:

• The developed IRMA is a highly sensitive and quantitative method for detecting anti-M antibodies.
• This IRMA offers improved detection capabilities, especially in challenging cases.
• The IRMA technique shows potential for broader application in detecting various organ-specific autoantibodies.