Mass spectrometric quantification of salivary metanephrines—A study in healthy subjects

• Salivary metanephrines can be detected with LC–MS/MS with sufficient sensitivity.
• Posture influences metanephrine concentrations in both plasma and saliva.
• Salivary metanephrines are not influenced by the use of a collection device.
• Salivary samples should be obtained while fasting for 30 min.
• No correlations are found between plasma and saliva metanephrine concentrations.

BackgroundDetermination of metanephrine (MN), normetanephrine (NMN), and 3-methoxytyramine (3-MT) in saliva may offer potential diagnostic advantages in diagnosing pheochromocytoma.MethodsIn this preliminary study, we determined metanephrine concentrations in saliva of healthy subjects and the relationship with simultaneously measured plasma metanephrines. We also studied the possible influence of pre-analytical conditions such as a collection device, awakening, posture, and eating on the salivary metanephrine levels.ResultsEleven healthy subjects were included. Fasting blood and saliva samples were collected in seated position and after 30 min of horizontal rest. Plasma and salivary MN, NMN, and 3-MT concentrations were determined using a high-performance liquid chromatography tandem mass spectrometric technique (LC–MS/MS) with automated solid phase extraction sample preparation. Metanephrines were detectable in saliva from all participants both in seated and supine position. No significant correlations were observed between the MN, NMN, and 3-MT concentrations in saliva and plasma in seated or supine position. Furthermore, there was no difference between MN, NMN, and 3-MT samples collected with or without a collection device.ConclusionMetanephrines can be detected in saliva with LC–MS/MS with sufficient sensitivity and precision. Our findings warrant evaluation of salivary metanephrine measurement as a novel laboratory tool in the work-up of patients suspected of having a pheochromocytoma.