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 Malmö from 1984 until January 1997.

Setting: Malmö 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.