Objective: The absence of specific markers can make the diagnosis of neuroimmune disorders difficult, making other biomarkers such as thyroid peroxidase antibodies (TPO-Abs) more relevant. Laboratory tests are susceptible to interference, especially those tests performed using immunoassay techniques. The effect of treatment with human intravenous immunoglobulin (IVIG) on the results of TPO-Abs assays has not been previously characterized.
Materials and methods: We analyzed TPO-Abs levels in 170 children monitored in the neuroimmune disease department of a tertiary hospital. We analyzed the characteristics of patients with increased TPO-Abs values and compared their progress with and without treatment.
Results: We found that 97% of patients with elevated TPO-Abs had received IVIG. After withdrawal from IVIG, a mean TPO-Abs decrease of 62.5% at 1 month was observed. The IVIG drug preparation was found to contain 1176 U/mL of TPO-Abs. An interferogram confirmed interference.
Conclusion: It is advisable to measure levels of TPO-Abs before starting immunotherapy and remain vigilant regarding possible interference in the event of unsubstantiated elevations of this analyte.
Keywords: autoimmune; immunoassay; interference; interferogram; nonspecific human intravenous immunoglobulin; thyroid peroxidase antibodies.
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