title: 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.
abstract: 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.
authors.affiliation: Hospices Civils de Lyon, Service Médecine Nucléaire, Groupement Hospitalier Est, Lyon, France.
authors.forename: Claire
authors.initials: C
authors.lastname: Bournaud
authors.forename: Anne
authors.initials: A
authors.lastname: Charrié
authors.forename: Cécile
authors.initials: C
authors.lastname: Nozières
authors.forename: Karim
authors.initials: K
authors.lastname: Chikh
authors.forename: Véronique
authors.initials: V
authors.lastname: Lapras
authors.forename: Marie-Laure
authors.initials: ML
authors.lastname: Denier
authors.forename: Christian
authors.initials: C
authors.lastname: Paulin
authors.forename: Myriam
authors.initials: M
authors.lastname: Decaussin-Petrucci
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Peix
authors.forename: Jean-Christophe
authors.initials: JC
authors.lastname: Lifante
authors.forename: Catherine
authors.initials: C
authors.lastname: Cornu
authors.forename: Céline
authors.initials: C
authors.lastname: Giraud
authors.forename: Jacques
authors.initials: J
authors.lastname: Orgiazzi
authors.forename: Françoise
authors.initials: F
authors.lastname: Borson-Chazot
mesh_terms: 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
chemical_list: D014408:Biomarkers, Tumor; D013954:Thyroglobulin