title: A cut-off value of basal serum calcitonin for detecting macroscopic medullary thyroid carcinoma.
abstract: OBJECTIVE
  Serum calcitonin (CT) level is used to detect medullary thyroid carcinoma (MTC), but the cut-off level is unclear. We aimed at identifying the optimal cut-off value of basal serum CT levels for detecting MTC.
  
  
  METHODS
  We retrospectively enrolled patients with hypercalcitoninemia (≥2·9 pmol/l) who had undergone thyroid ultrasonography (US) and subsequent work-up between 2001 and 2013 at Asan Medical Center. We divided patients into four groups: proven MTC (group 1, n = 93), pathologically proven non-MTC after surgery (group 2, n = 57), benign single nodule by cytology (group 3, n = 68) and patients without nodules on US (group 4, n = 24).
  
  
  METHODS
  Basal serum CT levels were evaluated.
  
  
  RESULTS
  The median CT level of group 1 (119·5 pmol/l) was significantly higher than those of other groups (4·0, 3·8 and 3·8 pmol/l, P < 0·001). When we adopted 19·0 pmol/l of CT level as a cut-off value, the sensitivity, specificity, and positive and negative predictive values were 77·4%, 98·7%, 97·3% and 87·8%, respectively. When we compared 29·2 pmol/l (100 pg/ml) and 19·0 pmol/l (65 pg/ml) as cut-off values, 19·0 pmol/l was more sensitive and accurate than 29·2 pmol/l. Factors associated with hypercalcitoninemia in non-MTC groups were autoimmune thyroiditis, chronic kidney disease, proton pump inhibitors and other malignancies. Serum CT levels tended to decrease spontaneously in non-MTC groups.
  
  
  CONCLUSIONS
  Basal serum CT levels higher than 19·0 pmol/l can be a useful cut-off value for detecting macroscopic MTC, even though values below 19·0 pmol/l cannot exclude the presence of MTC like small volume MTC or premalignant C-cell hyperplasia.
authors.affiliation: Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Hyemi
authors.initials: H
authors.lastname: Kwon
authors.forename: Won Gu
authors.initials: WG
authors.lastname: Kim
authors.forename: Yun Mi
authors.initials: YM
authors.lastname: Choi
authors.forename: Eun Kyung
authors.initials: EK
authors.lastname: Jang
authors.forename: Min Ji
authors.initials: MJ
authors.lastname: Jeon
authors.forename: Dong Eun
authors.initials: DE
authors.lastname: Song
authors.forename: Jung Hwan
authors.initials: JH
authors.lastname: Baek
authors.forename: Jin-Sook
authors.initials: JS
authors.lastname: Ryu
authors.forename: Suck Joon
authors.initials: SJ
authors.lastname: Hong
authors.forename: Tae Yong
authors.initials: TY
authors.lastname: Kim
authors.forename: Won Bae
authors.initials: WB
authors.lastname: Kim
authors.forename: Young Kee
authors.initials: YK
authors.lastname: Shong
mesh_terms: D014408:Biomarkers, Tumor / Q000378:metabolism; D002116:Calcitonin / Q000097:blood*; D018276:Carcinoma, Medullary / Q000097:blood / Q000151:congenital*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008495:Medical Oncology / Q000592:standards; D008875:Middle Aged; D018813:Multiple Endocrine Neoplasia Type 2a / Q000097:blood*; D011237:Predictive Value of Tests; D054328:Proton Pump Inhibitors / Q000627:therapeutic use; D051436:Renal Insufficiency, Chronic / Q000097:blood / Q000000981:diagnostic imaging; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013961:Thyroid Gland / Q000000981:diagnostic imaging; D013964:Thyroid Neoplasms / Q000097:blood*; D013967:Thyroiditis, Autoimmune / Q000097:blood / Q000000981:diagnostic imaging; D014463:Ultrasonography
chemical_list: D014408:Biomarkers, Tumor; D054328:Proton Pump Inhibitors; D002116:Calcitonin