Cut-off value for needle washout thyroglobulin in athyrotropic patients

Authors


  • This work was supported by a grant from Korea University. The authors have no other funding, financial relationships, or conflicts of interest to disclose. The authors have no other funding, financial relationships, or conflicts of interest to disclose.

Abstract

Objectives/Hypothesis:

The purpose of this study was to determine the appropriate cut-off value for fine needle aspiration-thyroglobulin (FNA-Tg) associated with postoperative recurrences and validate the diagnostic efficacy of FNA-Tg in patients after total thyroidectomy compared with concomitant cytology (C).

Study Design:

Retrospective.

Methods:

We retrospectively evaluated the results of ultrasound-guided FNAs performed for suspicious cervical lesions of 40 patients (male:female = 10:30; mean age, 44.0 years) after total thyroidectomy (mean duration, 89.1 months), to acquire the material for Tg and C analysis. After collection of the cytologic sample, we rinsed the same needle with 1 mL of normal saline for Tg radioimmunoassay.

Results:

Of 40 lesions (mean size, 0.89 cm; range, 0.3–3.5cm), 21 were confirmed as recurrences and 19 were nonrecurrences. The rates of nondiagnostic sampling and sensitivity and specificity of FNA-C when diagnostic sampling was obtained were 40% (16/40), 100% (14/14), and 90.0% (9/10), respectively. According to receiver operating characteristic analysis, the optimal cut-off value of FNA-Tg was 4.1 ng/mL (sensitivity, 100% [21/21]; specificity, 100% [19/19], P < .05). Furthermore, in 16 inconclusive lesions due to nondiagnostic cytologic results, the FNA-Tg results coincided with a final diagnosis (seven recurrences and nine nonrecurrences). The cases with maximum diameters <1 cm showed a significantly increased rate of nondiagnostic cytologic results, and the FNA-Tg results were more helpful than lesions ≥1 cm in diagnosing a recurrence (P < .05).

Conclusions:

Measurement of FNA-Tg is helpful for distinguishing recurrent from nonrecurrent lesions in the majority of patients who were previously treated for well-differentiated papillary thyroid carcinoma.

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