title: Thyroglobulin level in fine-needle aspirates for preoperative diagnosis of cervical lymph node metastasis in patients with papillary thyroid carcinoma: two different cutoff values according to serum thyroglobulin level.
abstract: BACKGROUND
  Measurement of thyroglobulin (Tg) in the washout fluid of fine-needle aspirates (FNA-Tg) is useful for diagnosis of lymph node (LN) metastasis in papillary thyroid carcinoma (PTC). However, the cutoff value of FNA-Tg in the preoperative state is not defined clearly. This study aimed to evaluate the optimal cutoff value of preoperative FNA-Tg according to serum Tg level.
  
  
  METHODS
  FNA-Tg was measured in 135 PTC patients (160 LNs) for preoperative diagnosis of cervical LN metastasis.
  
  
  RESULTS
  Of the 160 LNs, 119 (74%) were surgically removed and 110 (69%) were diagnosed as malignant. When we adopted a FNA-Tg of 1.0 μg/L as the cutoff value, the sensitivity and specificity were 99% and 76%, respectively. FNA-Tg levels were correlated with serum Tg levels (Pearson's coefficient 0.42, p=0.002) and the FNA-Tg levels of 12 of the 50 benign LNs were above 1.0 μg/L. We classified the LNs into two groups according to serum Tg level regardless of anti-Tg antibody status: a low Tg group (≤1.0 μg/L, n=22, 14%) and a high Tg group (>1.0 μg/L, n=138, 86%). In the low Tg group, the sensitivity and specificity of the FNA-Tg cutoff value of 1.0 μg/L were 93% and 100%, respectively. In the high Tg group, the sensitivity and specificity of the FNA-Tg cutoff value of 19.0 μg/L were 93% and 100%, respectively. A Tg ratio (FNA-Tg level divided by serum Tg level) of 0.5 gave an improved diagnostic performance (sensitivity, 98%; specificity, 98%) in the high Tg group.
  
  
  CONCLUSIONS
  FNA-Tg levels in the preoperative state are affected by serum Tg levels when they exceeded 1.0 μg/L. For the preoperative diagnosis of metastatic cervical LNs, it seems reasonable to employ different cutoff values of FNA-Tg depending on serum Tg levels. We propose the use of an optimal cutoff value of FNA-Tg of 1.0 μg/L in patients with low serum Tg levels and a Tg ratio of 0.5 in those with high serum Tg levels irrespective of thyroglobulin antibody status.
authors.affiliation: 1 Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine , Seoul, Korea.
authors.forename: Min Ji
authors.initials: MJ
authors.lastname: Jeon
authors.forename: Won Gu
authors.initials: WG
authors.lastname: Kim
authors.forename: Eun Kyung
authors.initials: EK
authors.lastname: Jang
authors.forename: Yun Mi
authors.initials: YM
authors.lastname: Choi
authors.forename: Yu-Mi
authors.initials: YM
authors.lastname: Lee
authors.forename: Tae-Yon
authors.initials: TY
authors.lastname: Sung
authors.forename: Jong Ho
authors.initials: JH
authors.lastname: Yoon
authors.forename: Ki-Wook
authors.initials: KW
authors.lastname: Chung
authors.forename: Suck Joon
authors.initials: SJ
authors.lastname: Hong
authors.forename: Jung Hwan
authors.initials: JH
authors.lastname: Baek
authors.forename: Jeong Hyun
authors.initials: JH
authors.lastname: Lee
authors.forename: Tae Yong
authors.initials: TY
authors.lastname: Kim
authors.forename: Young Kee
authors.initials: YK
authors.lastname: Shong
authors.forename: Won Bae
authors.initials: WB
authors.lastname: Kim
mesh_terms: D000328:Adult; D019540:Area Under Curve; D014408:Biomarkers, Tumor / Q000032:analysis* / Q000097:blood; D002277:Carcinoma / Q000097:blood / Q000737:chemistry* / Q000473:pathology / Q000556:secondary* / Q000601:surgery; D002291:Carcinoma, Papillary; D061765:Endoscopic Ultrasound-Guided Fine Needle Aspiration; D005260:Female; D006801:Humans; D008197:Lymph Node Excision; D008198:Lymph Nodes / Q000737:chemistry* / Q000473:pathology* / Q000601:surgery; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012372:ROC Curve; D015203:Reproducibility of Results; D013954:Thyroglobulin / Q000032:analysis* / Q000097:blood; D000077273:Thyroid Cancer, Papillary; D013964:Thyroid Neoplasms / Q000097:blood / Q000737:chemistry* / Q000473:pathology* / Q000601:surgery
chemical_list: D014408:Biomarkers, Tumor; D013954:Thyroglobulin