title: Comparison of Thyroglobulin Measurements Using Three Different Immunoassay Kits: A BRAMHS Tg-Plus RIA Kit, a BRAMHS hTg Sensitive Kryptor Kit, and a Beckman Coulter ACCESS Immunoassay Kit.
abstract: BACKGROUND
  Second-generation thyroglobulin immunometric assays (Tg-IMAs) have been developed with improved sensitivity. Our aim was to compare the diagnostic value of Tg-IMA measurements using a Kryptor (BRAHMS AG) kit (Tg-K) and an ACCESS (Beckman Coulter) kit (Tg-A) with that of the first-generation Tg measurement using a Tg-plus (BRAHMS AG) kit (Tg+).
  
  
  METHODS
  We enrolled 82 differentiated thyroid cancer patients who underwent total thyroidectomy with radioactive iodine remnant ablation and who underwent diagnostic whole body scan using recombinant human thyroid stimulating hormone (rhTSH). The Tg+, Tg-K, and Tg-A were measured before rhTSH administration during levothyroxine treatment (suppressed Tg) from the same sample. Serum Tg+ was measured after rhTSH stimulation (stimulated Tg).
  
  
  RESULTS
  Suppressed Tg+ was more significantly correlated with suppressed Tg-K (R²=0.919, P<0.001) than with suppressed Tg-A (R²=0.536, P<0.001). The optimal cut-off values of suppressed Tg+, Tg-K, and Tg-A for predicting stimulated Tg+ of 1 ng/mL were 0.3, 0.2, and 0.2 ng/mL, respectively. The sensitivity, specificity, and accuracy of suppressed Tg+ were 67%, 100%, and 90%, respectively; those of suppressed Tg-K were 83%, 90%, and 88%; those of suppressed Tg-A were 96%, 82%, and 87%, respectively. The positive predictive and negative predictive values of Tg+ were 100% and 87%, respectively; those of Tg-K were 79% and 92%; and those of Tg-A were 73% and 98%.
  
  
  CONCLUSIONS
  We could not clearly demonstrate which kit had better diagnostic performance after comparison of first-generation Tg measurements with Tg-IMA measurements. Also, there were kit-to-kit variations between Tg-IMA kits. Suppressed Tg measured by Tg-IMA was insufficient to completely substitute for a stimulated Tg measurement.
authors: Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors: Mijin
authors: http://orcid.org/0000-0002-1538-8859
authors: M
authors: Kim
authors: Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea. mj080332@gmail.com.
authors: Min Ji
authors: http://orcid.org/0000-0002-1297-107X
authors: MJ
authors: Jeon
authors: Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors: Won Gu
authors: WG
authors: Kim
authors: Department of Nuclear Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors: Jong Jin
authors: JJ
authors: Lee
authors: Department of Nuclear Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors: Jin Sook
authors: JS
authors: Ryu
authors: Department of Laboratory Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors: Eun Jung
authors: EJ
authors: Cho
authors: Department of Laboratory Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors: Dae Hyun
authors: DH
authors: Ko
authors: Department of Laboratory Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors: Woochang
authors: W
authors: Lee
authors: Department of Laboratory Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors: Sail
authors: S
authors: Chun
authors: Department of Laboratory Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors: Won Ki
authors: WK
authors: Min
authors: Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors: Tae Yong
authors: TY
authors: Kim
authors: Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors: Young Kee
authors: YK
authors: Shong
authors: Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors: Won Bae
authors: WB
authors: Kim
keywords: Anti-thyroglobulin; Differentiated thyroid cancer; Immunoassay; Thyroglobulin