THE PREDICTIVE VALUE OF DIAGNOSTIC-TESTS FOR PHEOCHROMOCYTOMA

Background. Ascertaining or excluding a pheochromocytoma may be diffic ult. The purpose of this study is to identify preoperative tests that are good predictors of a pheochromocytoma. Methods. Patients presumpti vely diagnosed with a pheochromocytoma based on clinical assessment, p lasma or urinary catecholamines, computed tomography, or magnetic reso nance imaging were analyzed. The sensitivity, specificity, positive, a nd negative predictive values were determined for each test based on t he pathologic finding of a pheochromocytoma. Data were analyzed wish S tudent's t test or Fisher's exact test. Results. Of 14 patients, seven had pathologically proven pheochromocytomas, whereas three had cortic al adenomas. In Sour patients, a pheochromocytoma was excluded by repe at testing. The 24-hour urinary mean metanephrine levels were signific antly different between patients with and without pheochromocytomas (5 .8 mu g vs 0.5 mu g, p = 0.05) and had the best positive predictive va lue (83%) and negative predictive value (100%) of the biochemical test s. T2-weighted magnetic resonance imaging had a 100% positive and nega tive predictive value. Age, sex, symptoms, blood pressur,e tumor locat ion, tumor size, and plasma catecholamine levels could not accurately predict or exclude a pheochromocytoma. Conclusions. T2-weighted magnet ic resonance imaging is the imaging study of choice for predicting a p heochromocytoma. The 24-hour urinary metanephrine level is the single best biochemical indicator of a pheochromocytoma. Plasma catecholamine levels and computed tomography are not helpful in diagnosing or exclu ding a pheochromocytoma.