DIAGNOSTIC SPECIFICITY OF SERUM CHROMOGRANIN-A FOR PHEOCHROMOCYTOMA IN PATIENTS WITH RENAL DYSFUNCTION

We assessed the clinical utility of serum chromogranin A (CgA) alone and in combination with plasma catecholamines in the diagnosis of pheochromocytoma in patients with mild to moderate renal impairment. The study population consisted of 44 normal subjects, 50 subjects with proven pheochromocytoma, and 82 subjects with hypertension (60 primary and 22 secondary) suspected but not proven to have the disease. In this highly selected group with high disease prevalence (38%), the overall sensitivity, specificity, accuracy, and positive and negative predictive values of serum CgA in the diagnosis of pheochromocytoma were 86%, 74%, 79%, 67%, and 94%, respectively. However, in patients with creatinine clearance less than 1.33 mL/s (80 mL/min), these values dropped to 85%, 50%, 59%, 38%, and 90%, respectively. The combination of plasma catecholamines and CgA provided the best overall specificity (95%), accuracy (88%), and positive predictive value (91%). In patients with a creatinine clearance of more than 1.33 mL/s, the combination gave a specificity of 98%, an accuracy of 89%, and a positive predictive value of 97%. These results show that serum CgA has poor diagnostic specificity in the diagnosis of pheochromocytoma when renal function is impaired. Combining CgA with plasma catecholamines provides a lower sensitivity, but excellent specificity, accuracy, and positive predictive value.