Larsson Anders, Gåfvels Mats, Karlsson Torbjörn
Section of Clinical Chemistry, Department of Medical Sciences, Uppsala University, Uppsala, Sweden.
Section of Haematology, Department of Medical Sciences, Uppsala University, Uppsala, Sweden.
Case Rep Oncol. 2020 Jun 16;13(2):680-682. doi: 10.1159/000507754. eCollection 2020 May-Aug.
Heterophilic antibodies but also M-components can interfere with laboratory tests causing erroneous results. We report the case of a 75-year-old man with myeloma and a monoclonal immunoglobulin component (M-component) that caused elevated thyroid-stimulating hormone (TSH) results. The M-component was of the IgG-lambda type. Thyroid markers were analyzed repeatedly, and there was a clear association between IgG concentrations and TSH values ( = 0.724). The highest TSH value was 75 mIU/L. Polyethylene glycol (PEG) precipitation of intact immunoglobulins was used to investigate if there was an antibody-related interference problem. The PEG treatment normalized the TSH value, showing that the cause of the elevated TSH result was due to interference caused by the M-component. In conclusion, it is important to remember that both heterophilic antibodies and M-components may cause erroneous results.
