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Sulfasalazine as a cause of false-positive elevation of urinary normetanephrine in patients with adrenal mass and suspected phaeochromocytoma: a diagnostic challenge
  1. Eunice Ter Zuling1,
  2. Miguel Debono2,
  3. Edmund Rab3 and
  4. Sabapathy Balasubramanian4
  1. 1General Surgery, Northern General Hospital, Sheffield, UK
  2. 2Department of Diabetes and Endocrinology, Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, UK
  3. 3Sheffield Laboratory Medicine, Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, UK
  4. 4Endocrine Surgery, Northern General Hospital, Sheffield, UK
  1. Correspondence to Eunice Ter Zuling; Eunicezuling.ter{at}


In patients with suspected phaeochromocytoma, biochemical screening of urine or blood for excess secretion catecholamines and/or their metabolites is performed. Elevated levels of catecholamines and metanephrines help in establishing the diagnosis of phaeochromocytoma. In two patients with adrenal lesions who were subjected to biochemical testing significantly elevated urinary normetanephrines appeared to establish the diagnosis of phaeochromocytoma. However, on subsequent investigations, this was demonstrated to be a ‘false positive’ finding. Both these patients were on sulfasalazine, an anti-inflammatory drug used in inflammatory bowel disease, rheumatoid arthritis and ankylosing spondylitis. Sulfasalazine can cause analytical interference in some assays for urinary normetanephrine and result in spuriously elevated levels, leading to misdiagnosis of phaeochromocytoma. In this report, one patient underwent adrenalectomy and another had conservative management.

Although this has been previously reported, increased awareness of the possibility of false-positive results on urinary metanephrines testing is important to reduce the potential for misdiagnosis and unnecessary treatment.

  • Endocrine system
  • Drugs: endocrine system
  • Adrenal disorders

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  • Contributors The following authors were responsible for drafting of the text, sourcing and editing of clinical images, investigation results, drawing original diagrams and algorithms, and critical revision for important intellectual content: ETZ, ER, SB. The following authors gave final approval of the manuscript: ETZ, ER, MD, SB.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Case reports provide a valuable learning resource for the scientific community and can indicate areas of interest for future research. They should not be used in isolation to guide treatment choices or public health policy.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.