Significance of serum angiotensin converting enzyme and gallium scan in noninvasive diagnosis of sarcoidosis.

Serum angiotensin converting enzyme (SACE) assays, chest roentgenograms and gallium scans were obtained in 28 patients with active sarcoidosis, two patients with resolved sarcoidosis and 43 nonsarcoid patients. In patients with active sarcoidosis, 23 had elevated SACE activity and 26 had diffuse uptake of gallium in the lung parenchyma. Normal SACE and gallium scans were found in patients with resolved sarcoidosis. None of the nonsarcoid patients had a combination of elevated SACE activity and diffuse pulmonary parenchymal uptake of gallium, although some had elevated SACE activity and abnormal gallium scans. These results suggest that combination of elevated SACE activity and diffuse accumulation of gallium in the lung parenchyma are suggestive of sarcoidosis. However, in view of the reports of abnormal gallium accumulation, and occasional elevation of SACE activity in silicosis, asbestosis and miliary tuberculosis, it is still necessary to require histological evidence of noncaseating granuloma to confirm the diagnosis of sarcoidosis.