Endogenous serum antibodies that interfere with a common thyroid hormone uptake assay: Characterization and prevalence

Detlef Ritter, Wayne Brown, Moon H. Nahm, Jack H. Ladenson, Mitchell G. Scott

Research output: Contribution to journalArticle

8 Scopus citations

Abstract

We identified individuals whose serum contained a substance that produced falsely decreased thyroid hormone (T)-uptake values determined by the Emit(TM) (Syva) procedure. Investigation of this interference was prompted by identification of a patient with T-uptake values inconsistent with clinical assessment. IgG depletion and supplementation studies with this patient's serum suggested that the interference was due to endogenous antibodies with specificity for the thyroxine-glucose-6-phosphate dehydrogenase conjugate in the Emit T-uptake assay. The prevalence of the interference was examined by prospectively comparing routine Emit T-uptake values of 1710 patients' samples to T-uptake values obtained by another method. Discrepant samples were also assayed by a radioactive binding triiodothyronine-uptake assay. We identified eight samples that had falsely decreased T-uptake values by Emit, for an overall prevalence of 0.46%. Among 45 consecutive patients with a T- uptake value <20%, five patients, or 11%, were falsely decreased by Emit and three of these were clearly due to an interfering IgG. We suggest that samples with abnormally low T-uptake values determined by the Emit method be confirmed by an alternative method.

Original languageEnglish
Pages (from-to)1940-1943
Number of pages4
JournalClinical chemistry
Volume40
Issue number10
DOIs
StatePublished - Jan 1 1994

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