Interpretation
Stress and acute, severe illness are associated with a physiological increase in metanephrines.
Drugs including beta-blockers, noradrenaline reuptake inhibitors and tricyclic antidepressants may raise in vivo metanephrine levels and make interpretation difficult.
Chronic renal failure may increase plasma metanephrines up to 2-fold.
Levels up to 2.5 fold URL may be attributable to stress of any acute illness, renal impairment or interfering medications, as listed above. Consider repeat testing after fasting, avoidance of caffeine and nicotine, omission of interfering drugs or after lying supine for 30 minutes.
Testing 24-hour urine metanephrines may also be considered.
Levels > 3 fold URL have a high positive predictive value for phaeochromocytoma or paraganglioma and patients should be referred to an Endocrinologist.
Plasma 3-methoxytyramine (3-MT), a dopamine metabolite associated with SDHx mutations with more malignant potential is available on request.
References/resources:
1. Eisenhoffer, G., Lattke, P., Herberg, M. et al. 2013. Reference intervals for plasma free metanephrines with an age adjustment for normetanephrine for optimized laboratory testing of phaeochromocytoma. Ann Clin Biochem, 50(1): 62-9.
2. Lenders, W., Duh, Q., Eisenhoffer, G. et al. 2014. Diagnosis and treatment of phaeochromocytoma and paraganglioma. JCEM , 6(1):1915-42.
3. Eisenhofer, G., Huysmans, F. et al. 2005. Plasma metanephrines in renal failure. Kidney Int, 67(2): 668-77.
4. Darr, R., Pamporaki, C., Peitzsch, M. et al. 2013. Biochemical diagnosis of phaeochromocytoma using plasma-free normetanephrine,metanephrine and methoxytyramine: importance of supine sampling under fasting conditions. Clinical Endocrinology, 80(4): 478-86.
Reference Intervals
| Age (years) |
Normetanephrine (pmol/L) |
Metanephrine (pmol/L) |
| 0-17 |
<900 |
<500 |
| 18-29 |
<1100 |
| 30-59 |
<1200 |
| 60+ |
<1400 |
Age related reference interval introduced March 2022. Reference ranges are for non-supine (seated/ambulatory) patients.
Test Method
Resin extraction, LC-Mass Spec detection
