Comparison of M22-based ELISA and Human-TSH-Receptor-based Luminescence Assay for the Measurement of Thyrotropin Receptor Antibodies in Patients with Thyroid Diseases

Abstract

Previously, a new procedure for measuring serum TSH receptor autoantibodies (TRAb) was reported in which the autoantibodies inhibit binding of a human monoclonal thyroid stimulating antibody M22 to TSHR-coated ELISA plate wells (TRAb ELISA). The aim of the present study was to evaluate the clinical performance of this assay in comparison to the second generation TRAb assay (TRAb LIA) based on the recombinant human TSH-receptor and chemiluminescence technology (TRAb LIA). Among the 158 patients, 84 patients suffered from Graves' disease (GD), 34 patients had Hashimoto's thyroiditis (HT), and 40 patients had euthyroid nodular thyroid disease (NTD) without signs of autoimmunity. TRAb measurements were performed according to the manufacturer's instructions. Out of 84 GD patients, 80 (95.2%) were TRAb positive as detected by the TRAb LIA. One GD patient had TRAb values within the grey zone (1.0-1.5 IU/l). All patients with HT and NTD were negative except in 6 (8.1%) cases whose TRAb values were within the grey zone. On the basis of the recommended cutoff value (TRAb 1.0 IU/l), the TRAb ELISA found 78 of 84 (92.9%) GD patients to be TRAb positive. None of the patients with HT, but two cases (5.0%) with NTD were TRAb positive. The diagnostic sensitivity of the TRAb LIA and TRAb ELISA assays was 95.2 and 92.9%, while the specificity was 100% and 97.3%, respectively. There was a close correlation (r=0.968, p<0.0001) between both assays in 84 patients with GD. Additionally, the between-run imprecision close to the cutoff limit was assessed. The calculated between-run coefficient of variation (CV) of the TRAb ELISA was 28.2% at the recommended cutoff value of 1.0 IU/l. Due to the evaluated imprecision data we propose a higher cutoff value correlating with a between-run CV of 20% (functional assay sensitivity). Our results indicate that due to a worse imprecision the TRAb ELISA has a slightly lower sensitivity and specificity compared to the TRAb LIA assay. These findings suggest that the M22 monoclonal antibody-based TRAb ELISA is not as reliable as other second generation TRAb assays in the diagnosis of Graves' diseases.

Accuracy of receptor-based methods for detection of thyrotropin-receptor autoantibodies: a new automated third-generation immunoassay shows higher analytical and clinical sensitivity for the differential diagnosis of hyperthyroidism

“…The aim of the present study was to evaluate the analytical sensitivity and precision and the diagnostic accuracy of a new fully automated system for the measurement of TRAb. Our results clearly show nd not determined that the analytical (functional) sensitivity of the RAD 120 system (0.4 IU/l) was higher than the mean of the secondgeneration (1.4 IU/l) [15,19,22,23], manual third-generation (1.1 IU/l) [26,30] and other automated third-generation assays (0.8 IU/l ) [32,37], probably because of the high analytical precision of the new system (Table 3). Within the last two decades huge efforts have been made to improve the first-generation methods for the measurement of TRAb, based on competitive binding of patients' TRAb and labelled bovine TSH to a soluble porcine TSHR [2].…”

“…The method is called the manual third-generation TRAb assay. However, the diagnostic accuracy of this manual ELISA is similar to that of the second-generation TRAb assay methods [24,26,[28][29][30][31] ( Table 1). The main limitation of these assays is their poor analytical sensitivity and imprecision due to the manual nature of the procedure.…”

“…This method is called the automated third-generation TRAb assay. Five recent studies using the unique commercial technology (Roche Diagnostics) have demonstrated that the diagnostic sensitivity (97.7%) and specificity (99.5%) are higher than those of the second-generation TRAb assays (94.5% and 98.4%, respectively; Table 1) [25,26,[33][34][35].…”

“…Several studies have shown that the clinical sensitivity of these assays increases to a mean of 95.9% (range 72.6-100%; Table 1) with a small decrease in specificity (97.9%, range 91.4-100%) [15,[17][18][19][22][23][24][25][26][27][28][29][30]. The recombinant human TSHR-based second-generation assay, in combination with labelled bovine TSH, is now considered the gold standard with the highest diagnostic accuracy.…”

Intermethod Variability in TSH-Receptor Antibody Measurement: Implication for the Diagnosis of Graves Disease and for the Follow-Up of Graves Ophthalmopathy

“…Third-generation TRAb assays, using a monoclonal thyroid stimulating antibody M22 which binds to a conformational epitope of TSH-R within the thyroid-stimulating hormone (TSH) binding pocket, have recently been described. Among them, the M22-biotin-based ELISA (8,9 ) and the automated Elecsys/Cobas electrochemiluminescence immunoassay (ECLIA) (10 ) have been developed. However, conflicting results have been reported on the advantages of the ELISA over earlier methods (8,9 ).…”