Impact of Thyroid Tissue Status on the Cut-Off Value of Lymph Node Fine-Needle Aspiration Thyroglobulin Measurements in Papillary Thyroid Cancer

Objective: To study the optimal cut-off value of thyroglobulin measurement in a fine-needle aspiration (FNA-Tg) in diagnosing malignant lymph nodes and benign lymph nodes (LNs) according to the thyroid tissue status.

Methods: A total of 517 LNs were aspirated: 401 preoperative LNs, 42 LNs after subtotal thyroidectomy and 74 suspected LNs after total thyroidectomy. The cut-off value of FNA-Tg was obtained from receiver operating characteristic (ROC) analysis. The cut-off value with the best diagnostic performance was then obtained by comparing different cut-off values from other studies.

Results: LN FNA-Tg levels differed between preoperative and total thyroid disease (p < 0.001) and subtotal thyroidectomy and total thyroidectomy (p = 0.03), but not between preoperative and subtotal thyroidectomy (p = 1.00). Accordingly, those 443 LNs with preoperative and subtotal thyroidectomy were compared to those 74 without thyroid tissue. The optimal cut-off value in thyroid tissue group was 19.4 ng/ml and the area under the ROC curve (AUC) was 0.95 (95% CI 0.92–0.97). The optimal cut-off value in thyroid tissue absence group was 1.2 ng/ml and the AUC was 0.93 (0.85–0.98). After the analysis and comparison of multiple cut-off values, the optimal diagnostic performance was still found to be 19.4 ng/ml and 1.2 ng/ml.

Conclusion: The influential factors of FNA-Tg are still controversial, and the optimal cut-off value of FNA-Tg can be determined based on the presence or absence of thyroid tissue. FNA-Tg can be used as an important auxiliary method for diagnosing cervical metastatic LNs of thyroid cancer.

Comparison of the diagnostic performances of US-guided fine needle aspiration cytology and thyroglobulin measurement for lymph node metastases in patients with differentiated thyroid carcinoma: a meta-analysis

OBJECTIVES

Ultrasound (US)-guided fine needle aspiration cytology (FNAC) and thyroglobulin measurement (FNA-Tg) are two common methods for confirming lymph node metastases (LNM) in patients with differentiated thyroid carcinoma (DTC). This study aimed at comparing the diagnostic performance of FNAC, FNA-Tg alone, and in combination by means of a meta-analysis.

METHODS

Eligible articles were selected according to predefined criteria, and their quality was evaluated as per the QUADAS-2 checklist. We calculated pooled sensitivity (Se), specificity (Sp), positive/negative likelihood ratio, and diagnostic odds ratio (DOR), and plotted the summary receiver operating characteristic (SROC) curve using the Meta-DiSc1.4 software.

RESULTS

Twenty-one studies pooling 1662 malignant and 1279 benign LNs from 2712 patients with DTC were included. The results showed that FNAC was more specific (pooled Sp, 0.98) while FNA-Tg was more sensitive (pooled Se, 0.94). FNAC and FNAC+FNA-Tg performed better postoperatively than FNA-Tg, while FNA-Tg performed better preoperatively. The combination of FNAC and FNA-Tg could achieve a better diagnostic performance than each alone (DOR 446.00, area under the curve [AUC] 0.9862), no matter preoperatively (DOR 378.14, AUC 0.9879) or postoperatively (DOR 788.72, AUC 0.9930). Besides, the combination of FNAC and FNA-Tg/serum-Tg ratio obtained a higher Sp (0.98) than the combination of FNAC and FNA-Tg.

CONCLUSION

The addition of FNA-Tg, especially the FNA-Tg/serum-Tg ratio, to FNAC could increase the diagnostic performance of LNM in both preoperative and postoperative patients with DTC. Since one test or test combinations could perform differently according to the clinical situation, the best-fitting test should be chosen accordingly.

KEY POINTS

• FNAC is more specific than FNA-Tg while FNA-Tg is more sensitive than FNAC. • The combination of FNAC and FNA-Tg could achieve a better diagnostic performance than either alone, no matter preoperatively or postoperatively. • The combination of FNAC and FNA-Tg/serum-Tg ratio could reach a higher Sp than the combination of FNAC and FNA-Tg.

Clinical application of the ultrasound-guided fine needle aspiration for thyroglobulin measurement to diagnose lymph node metastasis from differentiated thyroid carcinoma-literature review

Papillary thyroid carcinoma (PTC) generally has a good prognosis, but disease recurs in 25% to 30% of PTC patients and significantly reduces the survival rate. Lymph node metastasis (LNM) is reported in 20% to 50% of PTC patients, mainly in the neck, and 20% originates from recurrence. LNM of papillary thyroid carcinoma are a plausible prognostic factor to determine disease recurrence. Currently, fine needle lymph node aspiration for cytology (LN-FN-cytology) is the best modality to diagnose LNM but is limited by diagnostic sensitivity and sample error. Fine needle lymph node aspiration for thyroglobulin measurement (LN-FNA-Tg) could offer a reliable and quantitative diagnostic method for LNM. The combination of LN-FNA-cytology and LN-FNA-Tg could achieve almost 100% diagnostic sensitivity and specificity for LNM. Both treatment guidelines of the American Thyroid Association and European Thyroid Association recommend LN-FNA-Tg to diagnose LNM after total thyroidectomy. Diagnostic accuracy of the LN-FNA-Tg depends on optimal equipment, scanning protocol, skill, and experience of operators. Normal saline is mainly used for aspiration needle wash-out and buffer solution. And radioimmunoassay or immunoradiometric assay are widely used for the LN-FNA-Tg measurement. So far, there is no consensus about the diagnostic threshold of LN-FNA-Tg for positive LNM, but high LN-FNA-Tg, especially higher than 10 ng/mL, strongly favors LNM.

Diagnostic value of cytology, thyroglobulin, and combination of them in fine-needle aspiration of metastatic lymph nodes in patients with differentiated thyroid cancer: A systematic review and network meta-analysis

BACKGROUND

To investigate the diagnostic performance of cytology (fine-needle aspiration cytology [FNAC]), thyroglobulin (fine-needle aspiration thyroglobulin [FNA-Tg]), and combination of them in the washout of fine-needle aspiration for those patients who have suspicious metastatic lymph nodes of differentiated thyroid cancer.

METHODS

Databases, including PubMed, EMbase, Web of Science and Cochrane Library were searched up to June 2019. The quality assessment of diagnostic accuracy scale-2 was used to conduct quality assessments, and publication bias was evaluated using the Deeks funnel plot. STATA version 14.0 was used to perform the meta-analysis.

RESULTS

A total of 2257 patients with 2786 samples of suspicious metastatic lymph nodes of differentiated thyroid cancer were included in the meta-analysis. The results showed that the diagnostic value for detecting lymph node metastasis of differentiated thyroid cancer was as follows: combination of FNAC and FNA-Tg > FNA-Tg > FNAC. All differences of superiority among them are statistically significant. The sensitivity of the combination was 0.968 (95% confidence interval [CI]: 0.942-0.983), the specificity was 0.932 (95% CI: 0.856-0.969), the diagnostic score was 6.036 (95% CI: 4.892-7.181), the diagnostic odds ratio was 418.424 (95% CI: 133.167-1314.729), and the score of summary receiver operating characteristic was 0.99 (95% CI: 0.97-0.99).

CONCLUSIONS

The combination of FNAC and FNA-Tg is an excellent procedure in diagnosis of lymph nodes metastasis of patients with differentiated thyroid cancer, which should be highly recommended.

Cervical Lymph Node Fine-Needle Aspiration and Needle-Wash Thyroglobulin Reflex Test for Papillary Thyroid Carcinoma

Fine-needle aspiration (FNA) cytology coupled with needle-wash thyroglobulin (FNA-Tg) testing is recommended for cervical lymph node (LN) biopsies in patients with a history of papillary thyroid carcinoma (PTC). However, the procedure has not been standardized with the assay for FNA-Tg testing. A standard operating procedure (SOP) has been generated at our facility for cervical LN FNAs with Tg reflex testing on patients with a history of PTC. The procedure requires FNA cytology to be reviewed first, and all cases not positive for PTC are reflexed for FNA-Tg testing with the Beckman Access thyroglobulin assay. The thyroglobulin cutoff value is ≤ 1.0 ng/mL. From 2016 to 2017, 117 patients, including 71 women and 46 men, were identified as having a history of PTC. Patients' clinical characteristics were collected from medical records. A total of 143 LN biopsies were investigated for these patients. The results show that four out of 11 (36.4%) non-diagnostic LNs and five out of five (100%) atypical/suspicious LNs tested positive for FNA-Tg. Among these nine patients with positive thyroglobulin testing, LN metastases were proven histologically for all nine patients, and two patients were treated with LN ablation. Out of 68 LNs positive for PTC, three had FNA-Tg results. FNA-Tg testing was ordered for unknown reasons on two positive LNs (> 5000 ng/mL thyroglobulin) from one patient. The third LN was tested due to non-classic morphology, and the result was less than the cutoff value. Three patients with negative LN biopsies were tested to have elevated (> 1.0 ng/mL) thyroglobulin levels. One patient (FNA-Tg ng/mL) was proven to have multiple metastatic LNs through follow-up surgery. However, no positive LN was identified for the other two patients who had FNA-Tg level of 4.1 ng/mL and 37 ng/mL respectively. This is likely due to contamination, as these two patients had intact thyroids. In our practice, the FNA-Tg test is a very useful adjunct test to LN FNA specimens with a non-positive diagnosis in patients with a history of PTC. Furthermore, FNA-Tg testing increases diagnostic sensitivity among non-diagnostic and atypical/suspicious LNs. However, FNA-Tg testing should not substitute conventional cytology due to the following reasons: (1) false-negative thyroglobulin lab results; (2) PTC with loss of thyroglobulin expression; (3) LN metastasis from other origins; and (4) false-positive thyroglobulin testing due to blood contamination in patients who are not completely athyrotic.