Differences in serum thyroglobulin measurements by 3 commercial immunoradiometric assay kits and laboratory standardization using Certified Reference Material 457 (CRM-457).
BACKGROUND
Serum thyroglobulin (Tg) is essential in the follow-up of patients with differentiated thyroid carcinoma (DTC). However, interchangeability and standardization between Tg assays have not yet been achieved, even with the development of an international Tg standard (Certified Reference Material 457 [CRM-457]).


METHODS
Serum Tg from 30 DTC patients and serially diluted CRM-457 were measured using 3 different immunoradiometric assays (IRMA-1, IRMA-2, IRMA-3). The intraclass correlation coefficient (ICC) method was used to describe the concordance of each IRMA to CRM-457.


RESULTS
The serum Tg measured by 3 different IRMAs correlated well (r > .85, p < .0001), but clinically relevant discrepancies were found in 13.3% of patients. IRMA-3, which claims to be standardized to CRM-457, showed the best ICC (p(1) = .98) for the CRM-457.


CONCLUSIONS
Hospitals caring for patients with DTC should either set their own cutoffs for IRMAs for Tg based on their patient pools, or adopt IRMAs standardized to CRM-457 and calibrate their laboratory using CRM-457.
Lee
Ji In
JI
Division of Endocrinology and Metabolism, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.
Kim
Ji Young
JY
Choi
Joon Young
JY
Kim
Hee Kyung
HK
Jang
Hye Won
HW
Hur
Kyu Yeon
KY
Kim
Jae Hyeon
JH
Kim
Kwang-Won
KW
Chung
Jae Hoon
JH
Kim
Sun Wook
SW
D002291:Carcinoma, Papillary / Q000097:blood / Q000473:pathology / Q000601:surgery; D006801:Humans; D015592:Immunoradiometric Assay / Q000379:methods / Q000592:standards*; D008991:Monitoring, Physiologic / Q000379:methods; D011933:Reagent Kits, Diagnostic; D012015:Reference Standards; D015203:Reproducibility of Results; D013954:Thyroglobulin / Q000097:blood*; D013964:Thyroid Neoplasms / Q000097:blood* / Q000473:pathology / Q000601:surgery; D013965:Thyroidectomy / Q000379:methods
D011933:Reagent Kits, Diagnostic; D013954:Thyroglobulin