[TgAb interference with experimental Tg values detected by dilution curves].

Area of Science:

• Endocrinology
• Clinical Chemistry
• Immunology

Background:

• Thyroglobulin (Tg) is a key biomarker for differentiated thyroid cancer (DTC) management.
• Endogenous antithyroglobulin antibodies (TgAb) can interfere with Tg immunoassays, potentially affecting patient diagnosis and monitoring.
• Accurate Tg measurement is crucial for assessing treatment response and detecting recurrence in DTC patients.

Purpose of the Study:

• To investigate the interference of endogenous antithyroglobulin antibodies (TgAb) on thyroglobulin (Tg) measurements using dilution curves.
• To determine if TgAb levels can predict interference in experimental Tg values.

Main Methods:

• TgAb-positive and TgAb-negative sera were used to dilute Tg-containing sera from DTC patients.
• Tg levels were measured using immunometric assay (IMA).
• Dilution curves were generated by plotting experimental Tg values against expected Tg values to assess linearity and identify interference.

Main Results:

• Tg dilution curves using buffer were linear, serving as a control.
• Dilution with detectable TgAb serums yielded both linear and non-linear curves.
• Dilution with undetectable TgAb serums resulted in a higher proportion of non-linear curves, suggesting interference.

Conclusions:

• Dilution curves can serve as an indirect method to detect TgAb interference in Tg measurements.
• Undetectable TgAb levels may interfere with Tg assays, whereas detectable levels may not.
• TgAb levels alone are insufficient to predict interference in Tg testing.