An in vitro gallium-67 lung index for the evaluation of sarcoidosis

In the evaluation of the active alveolitis of pulmonary sarcoidosis, both the proportional lymphocyte count obtained by bronchoalveolar lavage and state of activation of the alveolar macrophage by gallium scanning are required. We injected 6 mCi (200 MBq) of 67Ga intravenously on 24 occasions in 13 patients with biopsy-proved sarcoidosis. Forty-eight hours later, patients were scanned with a rectilinear scanner and the generated scintigrams were evaluated using the NIH index. Seventy-two hours after injection, bronchoalveolar lavage was performed, and venous blood was sampled. The harvested lavage fluid was analyzed for absolute and proportional cell counts, and radioactivity was measured in blood and BAL fluid. An in vitro 67Ga index was generated and expressed as counts/100,000 alveolar macrophages/ml blood (mean, 0.0146 +/- 0.0087 SD). There was a significant relationship between the in vitro index and proportional lymphocyte BAL counts (r = 0.79; p less than 0.002) that was comparable to that obtained using the NIH index (r = 0.74; p less than 0.005). These data suggest that the in vitro index might offer a more objective assessment of 67Ga uptake by the lung, but this would require validation against clinical parameters in a prospective study.