Sulfasalazine related false positive urinary normetanephrine

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: MON 37-82-Pheochromocytoma & Paraganglioma
Monday, June 17, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board MON-50
Berna Imge Aydogan, Pinar Kubilay, Ali Riza Uysal and Sevim Güllü*
Ankara University Faculty of Medicine
Background :Initial evaluation for adrenal incidentaloma includes measurements of fractionated metanephrines in urine and provide a highly sensitive test for diagnosis of pheochromocytoma, but false-positive results remain to be a  problem.

Case Report: We report two patients admitted to Endocrinology department with adrenal incidentalomas. First patient  has had ulcerativite colitis for 9 years and ankylosing spondylitis for 2 years. During her colonoscopy a stricture was found and abdominal CT was performed. On abdominal CT a left adrenal mass, 29 mm in diameter was diagnosed . She was receiving sulfasalazine 3 gr/d for ankylosing spondilitis. Second patient  was receiving 4 gr/d sulfasalazine for the same indication with the first patient and he had an  15 mm left adrenal incidentaloma .

The  24-hour urinary catecholamines and metabolites were measured by high-performance liquid chromatography after urine specimens were acidified and hydrolyzed. First patient’s normetanephrine levels were measured twice and both were higher than the normal( 790.5 and 698 μg/d ; normal range 88-444 μg/d , 929 and 1290 mg/d creatinin).  Urinary metanephrine and adrenaline levels remained normal. Urinary noradrenaline levels were higher than the normal ( 69,7 and 96,4 μg/d; normal range 20-81 μg/d). Plasma chromogranin A level was normal.

Second patient’s urinary normetanephrine and vanillylmandelic acid level was higher than normal (817.4  μg/d; normal range 88-444 μg/d and 16,1 mg/d; normal range 1,8-6,7 mg/d) and other urinary cathecolamines and metabolites were normal. Both  patients were normotensive without antihypertensive medication. They had no history of hypertensive attacks, massive perspiration, palpitation, pallor or flushing. A false positive result in 24 hour urinary normetanephrine level was suspected but sulfasalazine treatment couldn’t stop  because of  active diseases in the spine.

Conclusions: We report biochemical misdiagnosis of pheochromocytoma in two patients being treated with sulfasalazine. Sulfasalazine is reported to cause false positive urinary cathecolamines Recognition of drugs that may interfere with assays of urinary normetanepfrine can avoid unnecessary surgical interventions and additional investigations.

Nothing to Disclose: BIA, PK, ARU, SG

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