title: Serum antithyroglobulin antibodies interfere with thyroglobulin detection in fine-needle aspirates of metastatic neck nodes in papillary thyroid carcinoma.
abstract: BACKGROUND
  It is recommended to measure thyroglobulin (Tg) levels in the needle washout fluids from fine-needle aspirations (FNAs) in patients with papillary thyroid carcinoma (PTC) who have ultrasonographically suspicious metastatic lymph nodes (LNs). However, it is not clear whether serum anti-Tg antibodies (TgAbs) interfere with the detection of Tg in needle washout fluids from FNAs (FNA-Tg).
  
  
  OBJECTIVE
  The objective of the study was to evaluate the influence of serum TgAbs on FNA-Tg detection.
  
  
  METHODS
  This retrospective observational cohort study enrolled 207 patients with conventional PTC in whom FNA-Tg values had been measured. All patients initially underwent total thyroidectomy and remnant ablation. FNA-Tg levels were measured from ultrasonographically suspicious metastatic LNs of 0.5 cm or greater in the longest diameter.
  
  
  RESULTS
  From 207 patients, 263 LNs were evaluated. Final histopathology was available for 92 LNs, of which 88 (96%) were malignant. FNA-Tg levels were lower in the LNs from serum TgAb-positive patients than in those from TgAb-negative patients (P < 0.001). In four of 13 metastatic LNs from TgAb-positive patients, the FNA-Tg levels were below 10 μg/liter including one in which both FNA-Tg and serum-stimulated Tg levels were below 1 μg/liter and stained positively for Tg in pathology. There was also one malignant LN with negative for FNA-Tg, serum-stimulated Tg, and serum TgAb but that nonetheless stained intensely for Tg. However, there were no malignant LNs with both negative cytology and negative FNA-Tg. A diagnosis based on FNA-Tg had a lower sensitivity and negative predictive value in the TgAb-positive group than in the TgAb-negative group.
  
  
  CONCLUSIONS
  FNA-Tg measurement is highly reliable in the diagnosis of neck metastases in PTC patients, even in cases of negative-stimulated Tg or positive TgAb. However, high-serum TgAb levels could interfere with FNA-Tg measurements and thereby result in falsely low FNA-Tg levels.
authors.affiliation: Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, 388-1 Pungnap-dong, Songpa-gu, Seoul 138-736, Korea.
authors.forename: Min Ji
authors.initials: MJ
authors.lastname: Jeon
authors.forename: Jee Won
authors.initials: JW
authors.lastname: Park
authors.forename: Ji Min
authors.initials: JM
authors.lastname: Han
authors.forename: Ji Hye
authors.initials: JH
authors.lastname: Yim
authors.forename: Dong Eun
authors.initials: DE
authors.lastname: Song
authors.forename: Gyungyub
authors.initials: G
authors.lastname: Gong
authors.forename: Tae Yong
authors.initials: TY
authors.lastname: Kim
authors.forename: Jung Hwan
authors.initials: JH
authors.lastname: Baek
authors.forename: Jeong Hyun
authors.initials: JH
authors.lastname: Lee
authors.forename: Young Kee
authors.initials: YK
authors.lastname: Shong
authors.forename: Won Bae
authors.initials: WB
authors.lastname: Kim
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001323:Autoantibodies / Q000009:adverse effects / Q000097:blood* / Q000494:pharmacology*; D044963:Biopsy, Fine-Needle; D001774:Blood Chemical Analysis; D002277:Carcinoma / Q000097:blood / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000473:pathology*; D002291:Carcinoma, Papillary; D002648:Child; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008198:Lymph Nodes / Q000473:pathology*; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D009333:Neck; D012189:Retrospective Studies; D013954:Thyroglobulin / Q000032:analysis* / Q000276:immunology; D000077273:Thyroid Cancer, Papillary; D013960:Thyroid Function Tests / Q000379:methods; D013964:Thyroid Neoplasms / Q000097:blood / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000473:pathology*; D014463:Ultrasonography; D055815:Young Adult
chemical_list: D001323:Autoantibodies; C006606:anti-thyroglobulin; D013954:Thyroglobulin