Assessing the activity of sarcoidosis: quantitative 67Ga-citrate imaging

Three different methods of quantitating 67Ga-citrate lung images--a visual index, a computer-assisted index, and the total-lung-to-background ratio--were compared in 71 studies of patients with biopsy-proven sarcoidosis. Fifty consecutive cases were analyzed independently by two different observers using all three methods. In 45 patients, both gallium lung scans and bronchoalveolar lavage were performed within 2 weeks. In these studies, each index was correlated with the cell differential in the bronchoalveolar lavage fluid. The total-lung-to-background ratio proved to be the simplest to perform; correlated best with the original visual index (r = 0.81, p less than 0.00001) and the percentage of lymphocytes obtained in bronchoalveolar lavage fluid (r = 0.39, p less than 0.004); and showed the lowest interobserver variation. Sensitivity for detecting active disease was 84% compared with 64% and 58% for the visual and computer-assisted indices, respectively, with no sacrifice in specificity.