Falsely elevated thyroid hormone levels due to anti-sheep antibody interference in an automated electrochemiluminescent immunoassay.

Full Abstract

We describe a 43-year-old woman with falsely increased thyroxine (T(4)) and triiodothyronine (T(3)) concentrations (total and index values) using a competitive electrochemiluminescent immunoassay, due to human anti-sheep antibodies. The thyrotropin (TSH) concentration was within normal limits. When specimens were re-tested by an immunoassay utilizing mouse antibodies, the total T(4) and T(3) concentrations were within normal limits. Removal of IgG by protein G column chromatography resulted in normalization of total T(4) and T(3) concentrations. In contrast, a mouse IgG column failed to normalize the elevated total T(4) and T(3) concentrations. Other immunoassays utilizing mouse monoclonal antibodies and rabbit antisera were unaffected, indicating that the interference was anti-sheep antibodies and not heterophile antibodies. We believe this is the first report of human anti-sheep antibodies causing falsely increased total and free T(4) and T(3) serum concentrations in competitive immunoassays using sheep antisera. Clinicians need to be aware of this potential problem since inaccurate thyroid function tests can lead to inappropriate treatment decisions.

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Author information

Author/s: Monchamp, Travis (T); Chopra, Inder J (IJ); Wah, David T (DT); Butch, Anthony W (AW);

Affiliation: Department of Medicine, Division of Endocrinology, Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California 90095-1732, USA.

Journal and publication information

Publication Type: Case Reports; Journal Article

Journal: Thyroid : official journal of the American Thyroid Association (Thyroid), published in United States. (Language: eng)

Reference: 2007-Mar; vol 17 (issue 3) : pp 271-5

Dates: Created 2007/03/26; Completed 2007/05/16;

PMID: 17381362, status: MEDLINE (last retrieval date: 12/26/2008)

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MeSH headings (categories)

This article was linked to the MESH Headings shown below.

Adult
Animals
Antibodies, Heterophile - biosynthesis
Electrochemistry - methods
False Positive Reactions
Female
Humans

Humans
Immunoassay - methods
Luminescence
Sheep
Thyroid Hormones - biosynthesis
Thyroxine - biosynthesis
Triiodothyronine - biosynthesis

Associated Chemicals: Antibodies, Heterophile (0) ; Thyroid Hormones (0) ; Triiodothyronine (6893-02-3) ; Thyroxine (7488-70-2)

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