Endocrinol Metab.  2016 Sep;31(3):462-468. 10.3803/EnM.2016.31.3.462.

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

• Kim M
• Jeon MJ
• Kim WG
• Lee JJ
• Ryu JS
• Cho EJ
• Ko DH
• Lee W
• Chun S
• Min WK
• Kim TY
• Shong YK
• Kim WB

• KMID: 2352987
• DOI: http://doi.org/10.3803/EnM.2016.31.3.462

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%.
CONCLUSION
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.

Keyword

Differentiated thyroid cancer; Thyroglobulin; Anti-thyroglobulin; Immunoassay

MeSH Terms

Humans
Immunoassay*
Iodine
Sensitivity and Specificity
Thyroglobulin*
Thyroid Neoplasms
Thyroidectomy
Thyrotropin
Thyrotropin Alfa
Thyroxine
Whole Body Imaging
Iodine
Thyroglobulin
Thyrotropin
Thyrotropin Alfa
Thyroxine

Figure

• 

  Fig. 1 Concordance between (A) suppressed Tg+ and suppressed Tg-K and (B) suppressed Tg+ and suppressed Tg-A in anti-thyroglobulin antibody negative patients. Tg, thyroglobulin; Tg+, Tg level measured with the BRAHMS Tg-plus RIA kit (BRAHMS AG); Tg-K, Tg level measured with the BRAMHS hTg sensitive Kryptor kit (BRAHMS AG); Tg-A, Tg level measured with the Beckman Coulter ACCESS immunoassay kit (Beckman Coulter).

• 

  Fig. 2 Concordance between stimulated Tg+ and (A) suppressed Tg+, (B) suppressed Tg-K, and (C) suppressed Tg-A as measured with each of the three different immunoassay kits in anti-thyroglobulin antibody negative patients. Tg, thyroglobulin; Tg+, Tg level measured with the BRAHMS Tg-plus RIA kit (BRAHMS AG); Tg-K, Tg level measured with the BRAMHS hTg sensitive Kryptor kit (BRAHMS AG); Tg-A, Tg level measured with the Beckman Coulter ACCESS immunoassay kit (Beckman Coulter).

• 

  Fig. 3 Sensitivity, specificity, accuracy, and positive predictive value (PPV) and negative predictive value (NPV) of (A) suppressed Tg+, (B) suppressed Tg-K, and (C) suppressed Tg-A in predicting positivity of stimulated Tg+. Tg, thyroglobulin; Tg+, Tg level measured with the BRAHMS Tg-plus RIA kit (BRAHMS AG); Tg-K, Tg level measured with the BRAMHS hTg sensitive Kryptor kit (BRAHMS AG); Tg-A, Tg level measured with the Beckman Coulter ACCESS immunoassay kit (Beckman Coulter).

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