title: Undetectable pre-ablation thyroglobulin levels in patients with differentiated thyroid cancer: it is not always what it seems.
abstract: OBJECTIVE
  To establish the frequency of U Tg (undetectable pre-ablation thyroglobulin) in TgAb- negative patients and to evaluate the outcome in the follow-up.
  
  
  METHODS
  We retrospectively reviewed 335 patients' records. Twenty eight patients (9%) had U Tg. Mean follow-up was 42 ± 38 months. All subjects had undergone total thyroidectomy, and lymph nodes were positive in 13 (46%) patients. Tg and TgAb levels were measured 4 weeks after surgery by IMA technology in hypothyroid state. No evidence of disease (NED) status was defined as undetectable (< 1 ng/mL) stimulated Tg and negative Tg-Ab and/or negative WBS, together with normal imaging studies.
  
  
  RESULTS
  Seventeen patients (61%) were considered with NED. Four patients (14%) had persistent disease (mediastinum, n = 1, lung n = 2, unknown n = 1), and 7 (25%) had detectable TgAb by other method during their follow-up.
  
  
  CONCLUSIONS
  U Tg levels usually is associated to a complete surgery. However, in a low percentage of patients, this may be related to false negative Tg or TgAb measurement.
authors.affiliation: Division of Endocrinology, Hospital de Clinicas, University of Buenos Aires, Buenos Aires, Argentina. fpitoia@intramed.net
authors.forename: Fabián
authors.initials: F
authors.lastname: Pitoia
authors.forename: Maria F
authors.initials: MF
authors.lastname: Bueno
authors.forename: Erika
authors.initials: E
authors.lastname: Abelleira
authors.forename: Maria E
authors.initials: ME
authors.lastname: Salvai
authors.forename: Liliana
authors.initials: L
authors.lastname: Bergoglio
authors.forename: Markus
authors.initials: M
authors.lastname: Luster
authors.forename: Hugo
authors.initials: H
authors.lastname: Niepomniszcze
mesh_terms: D055011:Ablation Techniques; D000328:Adult; D000368:Aged; D014408:Biomarkers, Tumor / Q000097:blood*; D002291:Carcinoma, Papillary / Q000097:blood* / Q000145:classification; D002454:Cell Differentiation; D005188:False Negative Reactions; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008198:Lymph Nodes / Q000473:pathology; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D013954:Thyroglobulin / Q000097:blood* / Q000276:immunology; D013961:Thyroid Gland / Q000601:surgery*; D013964:Thyroid Neoplasms / Q000097:blood* / Q000145:classification; D016896:Treatment Outcome
chemical_list: D014408:Biomarkers, Tumor; D013954:Thyroglobulin