Comparison of plasma metanephrines measured by a commercial immunoassay and urinary catecholamines in the diagnosis of pheochromocytoma.
BACKGROUND
The diagnosis of pheochromocytomas requires consideration among patients suffering from hypertension, unexplained spells, incidental adrenal masses, or a family history of pheochromocytoma. Accordingly, the diagnosis requires a biochemical test with high sensitivity and specificity.


OBJECTIVE
To compare plasma free metanephrines as measured by a commercial immunoassay and the 24-hour urinary excretion of catecholamines.


METHODS
Plasma free metanephrines were measured in 185 patients suspected of pheochromocytoma. Concomitant measurements of urinary catecholamines were performed in 115 patients. Based on clinical findings, imaging and biochemistry 11 cases were found; 9 were diagnosed with pheochromocytoma, one patient with paraganglioma and one patient with ganglioneuroma.


RESULTS
All patients with pheochromocytoma/paraganglioma had abnormally elevated concentrations of either plasma metanephrine or normetanephrine. The patient with ganglioneuroma had normal plasma metanephrine levels, corresponding to a sensitivity of 91%. In two patients where pheochromocytoma was excluded, plasma metanephrin or normetanephrine was above the reference level, corresponding to a specificity of 99%. Urinary catecholamines were determined in 10 of 11 patients with a positive diagnosis, and all 10 showed elevated levels of either urinary epinephrine or norepinephrine, including the patient with ganglioneuroma (equivalent to a sensitivity of 100%). Seven patients, in whom pheochromocytoma was excluded, had elevated urinary catecholamines (equivalent to a specificity of 94%).


CONCLUSIONS
Measurement of plasma free metanephrines by immunoassay appears to be a useful diagnostic test in patients suspected of pheochromocytoma, with a high specificity as compared with urinary catecholamines. The latter may result in fewer false-positive findings, an outcome which may be particularly troublesome.
Department of Endocrinology and Internal Medicine, & Medical Research Laboratories, Institute of Clinical Medicine, Aarhus University Hospital, Aarhus, Denmark.
Trine T
TT
Christensen
Jan
J
Frystyk
Per L
PL
Poulsen
D000293:Adolescent; D000310:Adrenal Gland Neoplasms / Q000097:blood / Q000175:diagnosis* / Q000473:pathology / Q000652:urine; D000311:Adrenal Glands / Q000473:pathology*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002395:Catecholamines / Q000652:urine; D002648:Child; D003718:Denmark; D004837:Epinephrine / Q000097:blood / Q000652:urine; D005260:Female; D005729:Ganglioneuroma / Q000097:blood / Q000175:diagnosis* / Q000473:pathology / Q000652:urine; D006801:Humans; D007118:Immunoassay; D008297:Male; D008676:Metanephrine / Q000097:blood*; D008875:Middle Aged; D009638:Norepinephrine / Q000097:blood / Q000652:urine; D009647:Normetanephrine / Q000097:blood / Q000652:urine; D010235:Paraganglioma / Q000097:blood / Q000175:diagnosis* / Q000473:pathology / Q000652:urine; D010673:Pheochromocytoma / Q000097:blood / Q000175:diagnosis* / Q000473:pathology / Q000652:urine; D012372:ROC Curve
D002395:Catecholamines; D009647:Normetanephrine; D008676:Metanephrine; D009638:Norepinephrine; D004837:Epinephrine