Utility of the clonidine test for the diagnosis of pheochromocytoma

Background. The clonidine test has been proposed as diagnostic biochemical test for patients with clinical suspicion of pheochromocytoma. Methods. The clonidine test was used in 80 patients with suspicion of pheoc hromocytoma ton account of suggestive clinical findings, increased levels o f metanephrines, increased plasma or urinary levels of catecholamines, or s uggestive images by ultrasonography or CT). Results. Surgery confirmed the diagnosis of pheochromocytoma in 16 patients . The highest sensitivity (62%) and specificity (46%) of the clonidine test corresponded to a brake degree of 5%, with a predictive negative value of 83%. The test was most useful in patients with increased basal plasma value s of catecholamines (sensitivity, 62%; specificity, 66%). Conclusions. The clonidine test can be useful for the diagnosis of pheochro mocytoma in patients with increased basal plasma levels of catecholamines a nd a brake degree lower than 5% at 180 minutes.