Armando Flores-Rebollar1. 1. Departamento de Medicina Interna, Instituto Nacional de Ciencias Médicas y Nutrición «Salvador Zubirán», Mexico City, Mexico. Electronic address: afcalatrava@yahoo.com.
Dear Editor,Yasri and Wiwanitki's letter on my case report speculates as to the association between the COVID-19 vaccination, blood hyperviscosity and thyroid dysfunction. No pathophysiological relationship between hyperviscosity and "aberrant thyroid function" has been reported. False thyroid hormone test results due to blood hyperviscosity should not be confounded with thyroid dysfunction.Hyperviscosity caused by acellular components (proteins), which may be monoclonal or polyclonal, are a known cause of potential interference in thyroid immunoassays. These correspond to uncommon entities including: Waldenström's macroglobulinaemia, cryoglobulinaemia and multiple myeloma, as well as rheumatic diseases associated with high rheumatoid factor levels. Paraprotein interference in immunoassays used to measure thyroid hormone and thyroid-stimulating hormone (TSH) levels has been extensively and specifically studied; although false results are mostly reported in total thyroid hormone levels,3, 4, 5, 6 any immunoassay used may be prone to interference. However, such interference is recognisable and does not indicate any thyroid function abnormality.
Ethics
All the procedures performed in the course of this retrospective study were carried out in accordance with institutional and national research committee ethical standards, and the study was conducted in accordance with World Health Organization (WHO) standards for biomedical and scientific research in humans. Case reports do not require independent ethics committee approval. Informed consent was obtained from and signed by the study participant.
Funding
This study received no specific funding from public, private or non-profit organisations.
Conflicts of interest
The author has no conflicts of interest to declare.