Correlation of sera concentra tions of thyroperoxidase a utoantibodies measured by two radioimmunoassays

Abstract

Introduction. Thyroid peroxidase-specific autoantibodies (TPO Abs) are mostly measured in patients with autoimmune thyroid diseases. The aim of this study was to compare TPO Ab concentrations measured by two radioimmunoassays. Material and methods. Our investigation included 38 patients. Sera concentrations of TPO Abs were measured by using Cis biointernational (France) and Immunotech (Czech Republic) assays. Results. Concentrations obtained by two assays were extensively different. The values measured by Cis biointernational assay were higher than ones obtained by Immunotech assay. The statistical arrangement of results showed the direct correlation between the two assays, with the coefficient of agreement R=0.6239 (p<0.001). The analysis of relative values (ratio of measured and upper limit values given by the manufacturer) demonstrated the statistically significant difference (p=0.003) between values measured by Cis biointernational (18.94?37.22) and by Immunotech assay (4.22?8.22) concerning the distinction between normal and raised concentrations of TPO Abs. The agreement of results (enhanced or normal TPO Ab concentrations in both tests) was shown in 30 sera samples (78.95%), but in residual 8 sera (21.05%) normal TPO Ab concentrations were obtained by Immunotech, and enchanced by Cis biointernational assay. There is no difference in capability of distinction between normal and pathological results between the two tests (?2=3.484, p>0.05). The highest concentration of TPO Ab measured by Cis biointernational assay was not the highest one in Immunotech assay, which might be a reflection of different specificity of antibodies used in two diagnostic tests. Conclusion. TPO Ab concentrations obtained by Cis biointernational and Immunotech assays are very different. In several sera samples, normal concentrations of TPO autoantibodies were obtained by Immunotech assay and enhanced by Cis biointernational assay. The highest value obtained by one is not the highest value measured by another assay we used.