Photo Credit: Nemes Laszlo

The following is a summary of “Plasma Metanephrines Yield Fewer False-Positive Results Than Urine Metanephrines in Patients With Obstructive Sleep Apnea,” published in the March 2024 issue of Endocrinology by King, et al.

Obstructive sleep apnea (OSA) increases nocturnal sympathetic activity, potentially leading to elevated metanephrines. However, this can complicate the evaluation for pheochromocytoma or paraganglioma (PPGL) due to false-positive test results. For a study, researchers sought to determine if morning plasma metanephrines yield fewer false-positive results than 24-hour urinary metanephrines in patients with OSA.

Patients undergoing polysomnography for suspected OSA were enrolled. Plasma-free and 24-hour urinary metanephrines were measured. Patients with elevated levels underwent repeat testing, imaging, and follow-up for PPGL diagnosis or exclusion.

About 76 patients completed testing, with 68 (89.5%) diagnosed with OSA; 19 (27.9%) had elevated metanephrines. One patient was diagnosed with bladder paraganglioma, while PPGL was ruled out in others. False-positive urinary metanephrines were more common (17 of 67, 25.4%) than plasma metanephrines (2 of 67, 3.0%) in patients with OSA (P < .01), especially in severe OSA (38.2% vs. 12.1% in moderate/mild OSA, P < .01). Both plasma and urinary metanephrines decreased after continuous positive airway pressure treatment. Severe OSA, obesity, and a family history of hypertension were positive predictors for false-positive urinary metanephrines on multivariable analysis.

Morning plasma metanephrines may be preferred over 24-hour urinary metanephrines in patients with OSA to avoid false-positive PPGL diagnoses. This is particularly relevant for patients with severe OSA, obesity, or a family history of hypertension to prevent unnecessary anxiety or follow-up.

Reference: academic.oup.com/jcem/article-abstract/109/3/844/7276434