Comparison of Some Different Methods for Analysis of Thyroid Autoantibodies: Importance of Thyroglobulin Autoantibodies

Abstract

Blood samples from 141 children and adolescents were used to evaluate differences between commercial kits and radioimmunoassay (RIA) methods for detecting thyroid autoantibodies. Thyroglobulin autoantibodies (Tg-Ab) were analyzed with a hemagglutination kit and a RIA; thyroid peroxidase autoantibodies (TPO-Ab) were measured with a gelagglutination assay and a RIA. The results of the antibody tests were compared with thyroid function tests (triiodothyronine [T3], thyroxine [T4], thyrotropin [TSH]) and with the results of ultrasound of the thyroid in antibody-positive patients. The correlation of antibody levels between the two methods was higher for TPO-Ab than for Tg-Ab. Moderate to high levels of TPO-Ab correlated to elevated TSH levels. Autoimmune thyroiditis (AIT) was found in 6 of the 141 children. The RIA-based thyroglobulin assay was the only test that identified autoantibodies in all 6 cases. In contrast, the hemagglutination kit thyroglobulin assay failed to identify 4 of the 6 AIT cases.

Definition of the upper reference limit for thyroglobulin antibodies according to the National Academy of Clinical Biochemistry guidelines: comparison of eleven different automated methods

“…Actually, to our knowledge, no similar data are present in literature: in the past, other studies faced the same topic but with small numbers of different analytical methods, most of which are no longer in use [9, 15–22, 29]. …”

“…Analytical limitations of serum TgAb assays have been reported in the context of thyroid autoimmunity diagnosis [9]. Despite standardization against the International Reference Preparation (IRP) MRC 65/93, several studies demonstrated a high variability in the analytical performances of different TgAb IMAs: large variation in limits of detection (LOD), FS, inter-method results, reference intervals with poor concordance between TgAb assays in patients with DTC [15–22]. The difficulty in standardization is in part due to the heterogeneous Tg immunoreactivity: differential splicing of Tg mRNA, various post-translational modifications, and alterations of biosynthesis regulation in thyroid tumor cells lead to exposure or masking of epitopes with resulting differences in Tg immunologic structure [23].…”

“…Besides Tg heterogeneity, assay discordance has also been assigned to various specificity of circulating TgAb in patient sera [6]. As a result, different TgAb values are obtained when the same serum is tested with different methods [15–22]. Finally, differences in assay reagents, above all the preparation of the antigen (Tg), definitely contribute to assay variability [1–12].…”

Glycopolymers from Saccharomyces Cerevisiae BIM Y-195 with Unusual Immunochemical Properties: Isolation, Structural Identification and Prediction of Their Role in Pathogenesis/Treatment of Autoimmune Thyroid Diseases

“…Concentrations of anti-TPO and anti-Tg in human serum of ATD patients are in range from 0.05 to 1.4 g/L (Beever et al, 1989) and do not exceed 10% of the concentration of total IgG. Probe "ATD" containing 1200 IU/mL anti-TPO plus 1500 IU/mL anti-Tg was used as single source of both autoantibodies, since just a few of HT patients have serum anti-TPO without anti-Tg (Lindberg et al, 2001). Probe "healthy" containing 25 IU/mL anti-TPO plus 52 IU/mL anti-Tg was used as a negative control, though it has slightly low concentrations of anti-TPO and anti-Tg, so called "natural autoantibodies", which commonly present in serum of healthy donors (Lleo et al, 2010).…”

Autoantibody profiling of patients with autoimmune thyroid disease using a new multiplexed immunoassay method

“…A simplification of the AITD diagnostic process using only the TPOAb assay, which is considered the most sensitive test, especially for Hashimoto's thyroiditis (HT), was recently proposed (3,4). However, this simplification is not universally accepted, because recent studies have reassessed the diagnostic role of TgAb, which has proved to be present alone in high concentrations in a fairly large percentage of patients suffering from HT (9)(10)(11), and seems to be evoked by specific epitopes present in the Tg molecule (12,13). However, this simplification is not universally accepted, because recent studies have reassessed the diagnostic role of TgAb, which has proved to be present alone in high concentrations in a fairly large percentage of patients suffering from HT (9)(10)(11), and seems to be evoked by specific epitopes present in the Tg molecule (12,13).…”