Familial Dysalbuminemic Hyperthyroxinemia and Thyroid Hormone Autoantibodies: Interference in Current Free Thyroid Hormone Assays

Abstract

The interference of familial dysalbuminemic hyperthyroxinemia (FDH), antithyroxine (anti-T₄) or antitriiodothyronine (anti-T₃) antibodies in serum free T₄ (FT₄) or free T₃ (FT₃) assays depends on the assay method: two-step immunoextraction, one-step labelled ligand (analogue or derivative tracer) or labelled antibody (solid-phase antigen-linked technique: SPALT) method. For FDH subjects, only FT₄ measurements by one two-step method gave reliable results in all cases. However, the overestimation was less marked with new SPALT assays than with previous analogue-based assays. In sera containing anti-T₄ antibodies, two-step assays and SPALT assays with a T₃-coated solid phase can be considered as reliable for FT₄ determination. All other methods including SPALT assays with a T₄-coated solid phase may give falsely high results. In sera containing anti-T₃ antibodies, SPALT FT₄ and FT₃ assays with a T₃-coated solid phase may give spuriously high values. Anti-T₃ antibodies do not interfere in two-step FT₃ assays and SPALT FT₃ assays with a T₂-coated solid phase, but may give high FT₃ values as measured by analogue or derivative methods. Moreover, SPALT free thyroid hormone assays may also be subject to interference from antibodies directed towards the assay solid phase.

Acute Abdomen in Henoch-Schönlein Purpura

“…Anti-T4 antibodies are well-known to account for a spuriously high free T4 result in the one-step analogue assay. The underlying mechanism is binding of the T4 analogue by antibody 3 . Antibodies are present in less than 1% of normal individuals 6 .…”

“…In adults, surgical intervention is seldom necessary 2 , whereas in children HSP is complicated by intussusception (2%), perforation (0.5%) and infarction (0.5%). Only one adult case of intestinal infarction secondary to HSP has been reported to our knowledge; that patient died 3 .…”

“…Interferon-alpha treatment is associated with autoimmune thyroid dysfunction 1,2 . Antibody to thyroxine (T4) can confuse the interpretation of thyroid function tests 3 .…”

LC-MS Quantification of Thyroid Hormones, Their Metabolites, Amino Acids and Neurotransmitters in Liver Tissue

“…However, due to the inherent complications of handling and disposing of radioactive materials, RIA in the (20). Nonspecific binding (30) and generation of autoantibodies (26) also can be sources of missquantification.…”

Discrepant Thyroid Function Tests in a Patient Treated with Interferon-Alpha

“…Interferon-alpha treatment is associated with autoimmune thyroid dysfunction 1,2 . Antibody to thyroxine (T4) can confuse the interpretation of thyroid function tests 3 .…”