Category: Adrenal Disorders

Monitor: 2

2 - FALSE POSITIVE URINARY METANEPHRINES - A CASE SERIES

Saturday, Apr 27
11:00 AM – 11:30 AM

Objective :

Despite the rareness of pheochromocytoma, availability of definitive treatment makes early diagnosis crucial to avoid life-threatening hypertension. It is essential for the clinicians to be familiar with the interpretation of 24-hour(hr) urine fractionated metanephrine screening test results to avoid unnecessary workup.


Methods : This is a retrospective, descriptive report of case series of two patient who had false positive urinary metanephrine during the endocrinology office visit.


Results :


Case 1: A 64-year-old female with the history of hypothyroidism and fibromyalgia presented with complaints of diaphoresis and palpitations. Her physical exam was unremarkable. Initial workup for hyperhidrosis resulted in normal thyroid function test (TFT), tryptase and 5-hydroxy indoleacetic acid (5-HIAA) level. Her 24-hr urine test showed metanephrines 69ug/24-hr (52-341), normetanephrine 760ug/24-hr (88-444) and total metanephrines 829ug/24-hr (140-785). On further questioning, she reported taking duloxetine for fibromyalgia. Considering the potential interference between antidepressant use and 24-hr urinary metanephrine testing, the test was repeated two weeks after discontinuation of the duloxetine with a normal result. Her repeat TFT showed suppressed TSH and symptoms resolved with subsequent levothyroxine dose reduction.




Case 2: A 73-year-old female presented with complaints of generalized hyperhidrosis, palpitations, and frequent loose stools. Initial workup resulted in normal TFT, and thyroid ultrasound. Endocrinopathy workup showed normal tryptase, 5-HIAA level, but elevated 24-hr fractionated urinary metanephrine 135ug/24-hr (52-341), normetanephrine 863ug/24-hr (88-444) and total metanephrine 998ug/24-hr (140-785). On review, the patient reported quetiapine use for insomnia. Repeat 24-hr urine fractionated metanephrine testing two weeks after discontinuation of the atypical antipsychotic (AAP) resulted normal. Thus, the abnormally elevated urine metanephrine was determined to be due to drug interference.


Discussion : Clinical practice guidelines recommend discontinuation of interfering medications, such as tricyclic antidepressant, levodopa, and adrenergic drugs, prior to 24-hr urinary fractionated metanephrine testing. AAP and serotonin-norepinephrine reuptake inhibitors are widely used but overlooked medication that leads to misleading test results and subsequent unnecessary imaging. Both cases discussed here had a false positive test as a result of medication interference.


Conclusion : The 24-hr urinary metanephrine test is widely used for pheochromocytoma screening and this report underscores the importance of reviewing home medications prior to testing in order to avoid unnecessary workup.

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Monisha Priyadarshini Kumar

Resident Physician, PGY2
Cleveland Clinic Akron General
Akron, Ohio

NA

Nairmeen Haller

Director of Research
Cleveland Clinic Akron General
AKRON, Ohio

NA

Michael Morocco

Attending Physician
Cleveland clinic Akron General
Akron, Ohio

NA

Monisha Priyadarshini Kumar

Monisha Priyadarshini Kumar

Resident Physician, PGY2
Cleveland Clinic Akron General
Akron, Ohio

NA