Undetectable Serum Thyroglobulin in Patients With Differentiated Thyroid Cancer: Antithyroglobulin Antibodies, Assay Limitation, or Other?
Authors' conclusion
Tg was detected by both Tg-IA and Tg-MS methods in the majority of FNAB washout fluid from patients with DTC LN metastases who exhibited undetectable serum Tg by Tg-IA and Tg-MS. The absence of serum Tg could not be completely explained by the presence of TgAb. These results suggest that, for a subset of patients with DTC LN metastases, the absence of detectable Tg in serum does not appear to be due to analytical limitations of current Tg assays or the presence of TgAb interference.
Study context
- Population
- Patients with differentiated thyroid cancer (DTC) lymph node metastases and undetectable serum thyroglobulin (Tg) by immunoassay (Tg-IA)
- Participants
- 42 patients
- Comparison
- TgAb+ vs TgAb-
- Outcome
- Detectable Tg in FNAB washout fluid
Methodological detailsspike-recovery experiments
- Spike-recovery experiments
Main finding
As reported in the abstract
Detectable Tg in fine needle aspiration biopsy (FNAB) washout fluid by Tg-IA
87%
Detectable Tg in FNAB washout fluid by Tg mass spectrometry (Tg-MS)
83%
Detectable serum TgAb
76%
No detectable serum TgAb
26%
Further findings
| Outcome | TgAb+ | TgAb- |
|---|---|---|
| Serum Tg spike recovery | mean 50% (range 12%–84%) | >94% |
| Tg-MS recovery (mean, range) | 96%, 70%-117% | — not stated in the abstract |
— not stated in the abstract
- Serum Tg spike recovery: TgAb+ value 50% is Tg-IA recovery
Serum Tg spike recovery
- Decreased Tg recovery by Tg-IA but not Tg-MS in TgAb+ serum; no interference in TgAb- serum
FNAB washout fluid Tg recovery
- No difference between TgAb- and TgAb+ patients
Original publication
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