title: A case of a false-positive anti-myeloperoxidase antibody ELISA in a patient with hypothyroidism.
abstract: We present a case of a false-positive anti-myeloperoxidase (MPO) antibody result on an ELISA in a patient with anti-thyroid microsomal antibody (TMA)-positive hypothyroidism. A 41-year-old woman presented with dyspnea on exertion. The initial evaluation revealed pericardial effusion associated with hypothyroidism. In addition, microscopic hematuria with normal renal function and positive cytoplasmic anti-neutrophil cytoplasmic antibodies (c-ANCA) on immunofluorescent assay were found. In further evaluation, elevated anti-TMA and MPO antibodies by ELISA. While no definite signs of vasculitis were present, the clinical state improved with thyroid hormone replacement and diuretics. Anti-MPO antibody was still positive in the follow-up tests, and microscopic hematuria persisted. On the basis of previous reports that thyroid peroxidase and MPO molecules contain cross-reactive epitopes that are exposed in denaturated molecules, we suggest that in a patient with anti-TMA-positive hypothyroidism, anti-MPO antibody might also be positive on ELISA without clinical signs of vasculitis.
authors: Department of Internal Medicine, Kyungpook National University School of Medicine, Daegu, Korea.
authors: Mi-Kyung
authors: MK
authors: Jin
authors: Kwan-Yong
authors: KY
authors: Seo
authors: Jin Young
authors: JY
authors: Kang
authors: Ji-Young
authors: JY
authors: Choi
authors: Se-Hee
authors: SH
authors: Yoon
authors: Yong-Lim
authors: YL
authors: Kim
authors: Dong-Il
authors: DI
authors: Won
authors: Sun-Hee
authors: SH
authors: Park