Biochemia Medica, Vol. 30 No. 2, 2020.
Other
https://doi.org/10.11613/BM.2020.021003
Case report of a phantom pheochromocytoma
Caroline M Joyce
; Department of Clinical Biochemistry, Cork University Hospital, Ireland
Audrey Melvin
; Department of Endocrinology, Cork University Hospital, Ireland
Paula M O’Shea
; Department of Clinical Biochemistry, Saolta University Health Care Group, Galway University Hospital, Ireland
Seán J Costelloe
; Department of Clinical Biochemistry, Cork University Hospital, Ireland
Domhnall J O’Halloran
; Department of Endocrinology, Cork University Hospital, Ireland
Abstract
Plasma free metanephrines or urinary fractionated metanephrines are the biochemical tests of choice for the diagnosis of pheochromocytoma as
they have greater sensitivity and specificity than catecholamines for pheochromocytoma detection. This case highlights the preanalytical factors
which can influence metanephrine measurement and cause a false positive result. It describes a patient with a high pre-test probability of pheochromocytoma
due to hypertension and a past medical history of adrenalectomy for a purported pheochromocytoma in her home country. When
biochemical screening revealed grossly elevated urine normetanephrine in the presence of a previously identified right adrenal lesion, there was
high clinical suspicion of a pheochromocytoma. However, functional imaging did not support this view which prompted additional testing with
plasma metanephrines. Results for plasma and urine metanephrines were discordant and preanalytical drug interference was suspected. Patient
medications were reviewed and sulfasalazine, an anti-inflammatory drug was identified as the most likely analytical interferent. Urinary fractionated
metanephrines were re-analysed using liquid chromatography tandem mass spectrometry (LC-MS/MS) and all metanephrines were within their
reference intervals. This case illustrates how method-specific analytical drug interference prompted unnecessary expensive imaging, heightened
patient anxiety and resulted in lengthy investigations for what turned out to be a phantom pheochromocytoma.
Keywords
case report; pheochromocytoma; metanephrines; false positive; sulfasalazine
Hrčak ID:
238917
URI
Publication date:
15.6.2020.
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