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J Endocrinol Invest. 2016 Oct;39(10):1159-65. doi: 10.1007/s40618-016-0478-9. Epub 2016 May 19.

Highly variable sensitivity of five binding and two bio-assays for TSH-receptor antibodies.

Author information

1
Molecular Thyroid Research Laboratory, Department of Medicine I, Johannes Gutenberg University (JGU) Medical Center, Mainz, Germany.
2
Endocrine Practice, Mainz, Germany.
3
Molecular Thyroid Research Laboratory, Department of Medicine I, Johannes Gutenberg University (JGU) Medical Center, Mainz, Germany. kahaly@ukmainz.de.

Abstract

PURPOSE:

TSH-receptor (TSHR) antibodies (Ab) can be measured with binding or bio-assays. Sensitivity and specificity of five binding and two bio-assays were compared.

METHODS:

TSHR-blocking (TBAb) and TSHR-stimulating (TSAb) Ab were measured with reporter bio-assays. Blocking activity was defined as percent inhibition of luciferase expression relative to induction with bTSH alone. TSAb was reported as percentage of specimen-to-reference ratio (SRR%). TSHR-binding inhibitory immunoglobulins (TBII) were measured with Kronus, Dynex, Kryptor, Cobas, and Immulite.

RESULTS:

Sixty patients with Graves' disease (GD), 20 with Hashimoto's thyroiditis (HT), and 20 healthy controls (C) were included. C tested negative in all assays (specificity 100 %) while all 60 hyperthyroid GD patients tested positive in the TSAb bio-assay (sensitivity 100 %). Among these 60 GD patients, 20 had low TSAb positivity (SRR% 140-279), but were TBII positive in only 20 (100 %), 7 (35 %), 9 (45 %), 11 (55 %), and 18 (90 %) using the Kronus, Dynex, Kryptor, Cobas, and Immulite, respectively. In 20 moderate TSAb-positive (SRR% 280-420) patients, TBII tested positive in 20 (100 %), 14 (70 %), 13 (65 %), 16 (80 %), and 19 (95 %), respectively. The high (SRR% > 420) TSAb-positive patients were all TBII positive. All 20 hypothyroid HT patients tested TBAb positive (sensitivity 100 %) in the bio-assay while they tested TBII positive in 20 (100 %), 18 (90 %), 20, 20, and 18, respectively. Results obtained with two luminometers correlated for TSAb positive (r = 0.99, p < 0.001), TBAb positive (r = 0.88, p < 0.001), and C (r = 0.86, p < 0.001). None of the binding assays differentiated between TSAb and TBAb.

CONCLUSIONS:

Sensitivity is highly variable between binding and bio-assays for TSHR-Abs.

KEYWORDS:

Binding assays; Bio-assays; Sensitivity; Specificity; TSH-receptor binding inhibitory immunoglobulins; Thyroid-blocking antibodies; Thyroid-stimulating antibodies

PMID:
27197966
DOI:
10.1007/s40618-016-0478-9
[Indexed for MEDLINE]

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