Detection of free plasma metanephrines seems to be the most exact method for biochemical diagnosis of pheochromocytoma, but their diagnostic efficacy in the common low-risk clinical settings is debated.
A cross-sectional multicentre study including 1260 subjects assessed the diagnostic efficacy of free plasma metanephrine and normetanephrine in low-risk patients screened for resistant or markedly accelerated hypertension, paroxysmal hypertension, ‘flushes’ and, in a small proportion, for adrenal incidentaloma or genetic predisposition to pheochromocytoma.
Pheochromocytoma was identified and verified by histology in 25 subjects (2%), with the diagnosis not confirmed by long-term follow-up or use of imaging techniques in the remaining 1235 individuals. The combined assay of free plasma metanephrines was a highly sensitive (100%) and specific (96.7%) measure, yielding a negative predictive value of 100%.
The satisfactory diagnostic efficacy of free plasma metanephrines allows their use as a single screening test in cases of suspected pheochromocytoma in the population with a low pretest probability.