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Original Article
- Comparison of Ultrasensitive and Highly Sensitive Assay to Predict Stimulated Thyroglobulin Levels Using Unstimulated Levels in Differentiated Thyroid Cancer Patients
- Jinsun Jang, Hyun Joo Kim, Seunggyun Ha, Kyong Yeun Jung, Gyeongseo Jung, Sun Wook Cho, Do Joon Park, Gi Jeong Cheon, Young Joo Park
- Received January 6, 2025 Accepted March 20, 2025 Published online June 5, 2025
- DOI: https://doi.org/10.3803/EnM.2025.2302 [Epub ahead of print]
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Abstract
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Supplementary Material
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ePub - Background
Thyroglobulin (Tg) measurement is an essential aspect of monitoring for differentiated thyroid cancer (DTC) patients. This study compared the performances of ultrasensitive Tg (ultraTg) and highly sensitive Tg (hsTg) assays in predicting stimulated Tg levels without thyroid-stimulating hormone stimulation.
Methods
Overall, 268 DTC patients who had undergone total thyroidectomy and either radioiodine treatment or I-123 diagnostic scanning were included. Unstimulated and stimulated Tg levels were measured using hsTg (BRAHMS Dynotest Tg-plus) and ultraTg (RIAKEY Tg immunoradiometric assay) assays. Correlations of each assay with the ability of unstimulated Tg levels to predict stimulated Tg ≥1 ng/mL were analyzed.
Results
hsTg and ultraTg showed a strong correlation (R=0.79, P<0.01); the correlation was weaker in Tg antibody-positive patients (R=0.52). UltraTg demonstrated higher sensitivity in predicting stimulated Tg ≥1 ng/mL compared with hsTg. The optimal cut-off for ultraTg was 0.12 ng/mL (sensitivity, 72.0%; specificity, 67.2%). hsTg at 0.105 ng/mL had lower sensitivity (39.8%) but higher specificity (91.5%). Eight discordant cases with low hsTg (<0.2 ng/mL) but elevated ultraTg (>0.23 ng/mL) were identified; three developed structural recurrence within 3.4 to 5.8 years. Two patients had an excellent response according to hsTg but an indeterminate or biochemical incomplete response according to ultraTg.
Conclusion
UltraTg demonstrated higher sensitivity in predicting positive stimulated Tg levels and potential recurrence compared with hsTg. However, its lower specificity may lead to more frequent classifications of biochemical incomplete response. UltraTg may be beneficial in clinically suspicious cases where hsTg falls below the cut-off, but its broader applicability requires further investigation.
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