Diagnostic Accuracy of Salivary Metanephrines in Pheochromocytomas and Paragangliomas

Background: Measurements of plasma free metanephrines are recommended for diagnosing pheochromocytomas and paragangliomas (PPGL). Metanephrines can be detected in saliva with LC-MS/MS with sufficient analytical sensitivity and precision. Because collecting saliva is noninvasive and less cumbersome than plasma or urine sampling, we assessed the diagnostic accuracy of salivary metanephrines in diagnosing PPGL. Methods: This 2-center study included 118 healthy participants (44 men; mean age: 33 years (range: 19-74 years)), 44 patients with PPGL, and 54 patients suspected of PPGL. Metanephrines were quantified in plasma and saliva using LC-MS/MS. Diagnostic accuracy; correlation between plasma and salivary metanephrines; and potential factors influencing salivary metanephrines, including age, sex, and posture during sampling, were assessed. Results: Salivary metanephrines were significantly higher in patients with PPGL compared with healthy participants (metanephrine (MN): 0.19 vs 0.09 nmol/L, P<0.001; normetanephrine (NMN): 2.90 vs 0.49 nmol/L, P<0.001). The diagnostic sensitivity and specificity of salivary metanephrines were 89% and 87%, respectively. Diagnostic accuracy of salivary metanephrines was 88%, with an area under the ROC curve of 0.880. We found a significant correlation between plasma and salivary metanephrines (Pearson correlation coefficient: MN, 0.86, P<0.001; NMN, 0.83, P<0.001). Salivary NMN concentrations were higher when collected in a seated position compared with supine (P<0.001) and increased with age (P<0.001). CONCLUSIONS: Salivary metanephrines are a promising tool in the biochemical diagnosis of PPGL. Salivary metanephrines correlate with plasma free metanephrines and are increased in patients with PPGL. At this time, however, salivary metanephrines cannot replace measurement of plasma free metanephrines.

Automated summary

The study suggests that salivary metanephrines have high sensitivity and accuracy in diagnosing PPGL, with a significant correlation to plasma metanephrines. However, salivary metanephrines cannot fully replace the measurement of plasma free metanephrines at present.