Metaiodobenzylguanidine (MIBG) scintigraphy and computed tomography (CT) in clinical practice. Primary and secondary evaluation for localization of phaeochromocytomas

Objective. To determine the diagnostic value of metaiodobenzylguanidine (MI BG) scintigraphy compared with computed tomography (CT) for the localizatio n of phaeochromocytomas in clinical practice. Design. Retrospective comparison between MIBG scintigrams and CT for locali zation of phaeochromocytomas in all patients successively examined with MIB G scintigraphy in Malmo from 1984 until January 1997. Setting. Malmo University Hospital, Sweden. Subjects. Sixty-four patients with clinically suspected phaeochromocytomas. Main outcome measures. MIBG scintigrams and CTs classified as positive or n egative based on original interpretations (primary evaluation) and in a sec ondary evaluation by one blinded examiner are assessed through histological confirmation or clinical rule out of phaeochromocytomas. Results. Twenty-five patients had surgically removed phaeochromocytomas. Th e remaining 39 patients had no proof of phaeochromocytomas. In the secondar y evaluation, sensitivity for MIBG scintigraphy was 88%, (22/25) and for CT was 100%, (25/25). The specificity for MIBG scintigraphy was 89%, (35/39) but only 50%, for CT (18/36). Two out of a total of six extra-adrenal tumou rs were amongst the false-negative MIBG scintigrams. Conclusions. MIBG scintigraphy for the localization of phaeochromocytomas i s superior to CT as far as specificity, whereas CT has a higher sensitivity . After biochemical diagnosis. CT will detect most phaeochromocytomas. MIBG scintigraphy can be of value in patients who show inconclusive results wit h biochemical testing and CT.