Thyroglobulin measurement. Techniques, clinical benefits, and pitfalls

Area of Science:

• Endocrinology
• Clinical Chemistry
• Oncology

Background:

• Serum thyroglobulin (Tg) measurement is vital for monitoring differentiated thyroid carcinoma (DTC).
• Maintaining precision and reliability in Tg assays is challenging due to long monitoring intervals and method variability.
• Intermethod differences in Tg measurements can approach 30%, impacting diagnostic accuracy.

Purpose of the Study:

• To highlight the critical importance of valid and reliable serum Tg measurements for accurate DTC diagnosis and cost-effective management.
• To inform physicians about factors influencing Tg assay validity, including method dependency and TgAb interference.
• To provide guidance on selecting appropriate laboratories and interpreting Tg results, especially in TgAb-positive patients.

Main Methods:

• Review of current methodologies and standardization efforts for serum Tg assays.
• Discussion of factors affecting assay sensitivity and specificity, including TgAb interference.
• Emphasis on the need for consistent laboratory methods and potential for serum banking for remeasurement.

Main Results:

• Serum Tg measurement validity is method-dependent, with significant intermethod variations persisting even after standardization.
• Thyroglobulin antibody (TgAb) interference can lead to under- or overestimation of total serum Tg levels depending on the immunoassay method used.
• Consistent serial Tg measurements by the same method in the same laboratory are essential for reliable patient monitoring.

Conclusions:

• Physicians must be aware of method-specific Tg assay limitations and TgAb interference.
• Careful laboratory selection, use of sensitive TgAb immunoassays, and consistent testing protocols are crucial for accurate DTC management.
• High-quality, reproducible Tg measurements improve cost-effectiveness by enabling risk stratification and targeted use of expensive diagnostic procedures.