Thyroglobulin measurement in fine-needle aspirates of lymph nodes in patients with differentiated thyroid cancer: a simple definition of the threshold value, with emphasis on potential pitfalls of the method.
BACKGROUND
Thyroglobulin measurements in fine-needle aspirate (FNA-Tg) is an accurate method for the diagnosis of lymph node metastasis in differentiated thyroid carcinoma. The goal of this study is to determine the most appropriate diagnostic threshold value for FNA-Tg.


METHODS
Ultrasound-guided fine-needle aspiration-cytology (FNA-C) and FNA-Tg were performed on suspicious lymph nodes in 114 consecutive patients with thyroid cancer prior to thyroidectomy (n=13) or during follow-up (n=93), and in 16 control subjects. Functional sensitivity of the thyroglobulin assay was 0.7 ng/mL. Sensitivity and specificity of FNA-Tg and FNA-C were determined for different cut-off values within a range of 0.69-1.34 nanogram/punction (ng/p) using receiver operating characteristic curve analysis.


RESULTS
The FNA-Tg cut-off value of 0.93 ng/p offers the best diagnostic performances: 94.2% sensitivity, 97.8% specificity. FNA-C showed 100% specificity in diagnostic samples, but low sensitivity of 71% due primarily to inadequate samples. Combining FNA-C and FNA-Tg resulted in 98% sensitivity and 100% specificity.


CONCLUSIONS
A unique threshold of 0.93 ng/p gives high sensitivity and specificity, even in non-thyroidectomized patients. However, since false negative results may be observed in poorly differentiated thyroid cancer, FNA-C should remain combined to FNA-Tg.
Bournaud
Claire
C
Hospices Civils de Lyon, Service Médecine Nucléaire, Groupement Hospitalier Est, Lyon, France.
Charrié
Anne
A
Nozières
Cécile
C
Chikh
Karim
K
Lapras
Véronique
V
Denier
Marie-Laure
ML
Paulin
Christian
C
Decaussin-Petrucci
Myriam
M
Peix
Jean-Louis
JL
Lifante
Jean-Christophe
JC
Cornu
Catherine
C
Giraud
Céline
C
Orgiazzi
Jacques
J
Borson-Chazot
Françoise
F
D000328:Adult; D014408:Biomarkers, Tumor / Q000032:analysis*; D044963:Biopsy, Fine-Needle / Q000379:methods*; D003937:Diagnosis, Differential; D005188:False Negative Reactions; D005260:Female; D006801:Humans; D008198:Lymph Nodes / Q000378:metabolism / Q000473:pathology* / Q000601:surgery; D008207:Lymphatic Metastasis / Q000175:diagnosis; D008297:Male; D008875:Middle Aged; D012372:ROC Curve; D012680:Sensitivity and Specificity; D013954:Thyroglobulin / Q000032:analysis*; D013964:Thyroid Neoplasms / Q000473:pathology* / Q000601:surgery; D013965:Thyroidectomy
D014408:Biomarkers, Tumor; D013954:Thyroglobulin