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 (MIBG) scintigraphy compared with computed tomography (CT) for the localization of phaeochromocytomas in clinical practice. Design. Retrospective comparison between MIBG scintigrams and CT for localization of phaeochromocytomas in all patients successively examined with MIBG 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 negative based on original interpretations (primary evaluation) and in a secondary evaluation by one blinded examiner are assessed through histological confirmation or clinical rule out of phaeochromocytomas. Results. Twenty-five patients had surgically removed phaeochromocytomas. The remaining 39 patients had no proof of phaeochromocytomas. In the secondary 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 tumours were amongst the false-negative MIBG scintigrams. Conclusions. MIBG scintigraphy for the localization of phaeochromocytomas is 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 with biochemical testing and CT.