J Lab Med Qual Assur.  2016 Dec;38(4):243-248. 10.15263/jlmqa.2016.38.4.243.

Assessment of the Precision and Functional Sensitivity of Two Thyroglobulin Assays: Comparison of the Second-Generation Roche Electrochemiluminescent Immunoassay and BRAHAMS Radioimmunoassay

• Kwon A
• Lee EH
• Lee YK
• Kang HJ

• KMID: 2368468
• DOI: http://doi.org/10.15263/jlmqa.2016.38.4.243

Abstract

BACKGROUND
Thyroglobulin (Tg) is the primary biochemical marker used to monitor patients with differentiated thyroid cancer (DTC) for residual or recurrent disease after total thyroidectomy, as only normal or well-differentiated malignant thyroid cells produce Tg. Here, we evaluated the precision and functional sensitivity (FS) of a recently developed highly sensitive Tg (hsTg) electrochemiluminescent immunoassay (ECLIA) and compared it to that of the radioimmunoassay (RIA) method using pooled human serum with low levels of Tg.
METHODS
For the ECLIA method, the Elecsys Tg II kit (Roche Diagnostics, Germany) was used with an E170 analyzer (Roche Diagnostics). For the RIA method, the Tg-plus-RIA kit (BRAHAMS, Germany) was used with a Cobra Quantum gamma counter (Packard Instrument Company, USA). The precision and limit of detection (LOD) were determined according to the Clinical and Laboratory Standards Institute (CLSI) guidelines. FS was determined using a modification of the CLSI guideline.
RESULTS
The total precision of the hsTg ECLIA and RIA methods was 9.6% and 48.2%, respectively. The manufacturer-reported LOD was verified by the hsTg ECLIA (0.04 ng/mL), but not by the RIA method (>0.08 ng/mL). The hsTg ECLIA showed better FS (0.04 ng/mL at a coefficient of variation [CV] of 10%) than the RIA method (0.37 ng/mL at a CV of 20%).
CONCLUSIONS
Thus, the hsTg ECLIA performed better than the RIA method in terms of FS, which is extremely important for the early detection of residual or recurrent disease in DTC patients after total thyroidectomy. The excellent performance of the hsTg ECLIA could allow for clinical Tg measurement without thyroid-stimulating hormone stimulation, in contrast to the insufficient performance of the RIA method.

Keyword

Thyroglobulin; Second-generation; Functional sensitivity; Radioimmunoassay; Comparison

MeSH Terms

Biomarkers
Elapidae
Humans
Immunoassay*
Limit of Detection
Methods
Radioimmunoassay*
Thyroglobulin*
Thyroid Gland
Thyroid Neoplasms
Thyroidectomy
Thyrotropin
Biomarkers
Thyroglobulin
Thyrotropin