Lessons from an unpleasant surprise: a biochemical strategy for the diagnosis of pheochromocytoma

Objective To audit the performances of the analytes used in the diagnosis o f pheochromocytoma and to present a graphical guideline to help the diagnos is. Design A 5 year retrospective study. Settings Laboratory and departments of a university hospital. Participants In-patients, suspected of bearing a pheochromocytoma, were inv estigated for urinary metanephrines and catecholamines (photometric method) and vanillylmandelic acid, fractionated catecholamines and metanephrines [ high pressure liquid chromatography (HPLC) coupled to electrochemical detec tion (ED)] urinary excretion. Main outcome Patients with a pheochromocytoma (24 out of 2003 patients) wer e diagnosed by the combination of normetanephrine and metanephrine determin ation. Results All analytes but dopamine were significantly elevated in patients w ith a pheochromocytoma. The area under the receiver operating characteristi cs (ROC) curves were the highest for total metanephrines, normetanephrine a nd metanephrine determinations, Because of analytical interferences in the metanephrines determination, the normetanephrine and metanephrine performed better, It is noteworthy that all pheochromocytomas had either normetaneph rine or metanephrine levels above their respective optimal threshold (sensi tivity 100%). The best optimal threshold performance was reached by the mea n of three daily samples. Total or fractionated catecholamines or vanillylm andelic acid were less accurate tools. Conclusion Amongst urinary tests, the combined use of HPLC/ED determination of normetanephrine and metanephrine seems the most effective screening str ategy for the diagnosis of pheochromocytoma, The older total metanephrine p hotometric assay is grieved by analytical interferences.