Study to Identify Causes of Interference of the Plasma Free Metanephrine Test

Researchers reviewed data from 460 people who did not have these tumours and found that the test was generally very reliable, with false-positive results occurring in only 7% of cases. Most chronic illnesses, such as diabetes, heart disease, and kidney disease, did not independently affect the test results. However, a group of antidepressant medicines known as norepinephrine reuptake blockers (including some SNRIs and tricyclic antidepressants) could raise levels of certain test markers, especially when taken at higher doses, making results appear abnormal when no tumour was present. Smoking and some antipsychotic medicines also affected one of the markers tested. The authors conclude that plasma free metanephrine testing remains a highly dependable way to screen for these tumours, but doctors should interpret results carefully in people taking specific antidepressants, particularly at moderate or high doses.

Lara M Knigge, Kristin Potthoff, Georgiana Constantinescu, Sybille Fuld, Karolina Zawadzka, Ermal Tahirukaj, Stefan Bornstein, Jacques W M Lenders, Graeme Eisenhofer, Christina Pamporaki; Determinants of false-positive plasma free metanephrines and methoxytyramine: the role of medications and chronic disease. Endocr Relat Cancer 1 May 2026; 33 (5): e250549. https://doi.org/10.1530/ERC-25-0549; summarised using AI and checked by the AMEND Medical Advisory Team
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