Lung function and disease activity in sarcoidosis - Disease activity in sarcoidosis

In sarcoidosis the lung clearance of inhaled Tc-99m-labelled diethylene triamine pentaacetic acid (DTPA) is often abnormal. Few studies related the lung clearance of Tc-99m-DTPA to the results of other lung function tests and/or disease activity parameters. This study describes the relationship in sarcoidosis between the lung clearance of Tc-99m-DTPA measured over 180 minutes, and a set of function tests comprising lung volumes and lung mechanics as well as arterial blood gases. Disease activity was assessed with serum angiotensin-converting enzyme (SACE) and Ga-67 scintigraphy. Measurements of lung clearance, spirometry and SACE were thus performed in 41 never-smoking patients with radiologic signs of intrathoracic sarcoidosis. In 32 patients a Ga-67 scan was obtained. The clearance of Tc-99m-DTPA was abnormal in 23 patients. Either an abnormally fast mono-exponential clearance or a bi-exponential clearance course was disclosed. In 17 of these patients, dynamic spirometry was normal. The Ga-67 scan was abnormal in 15 patients. There was a significant association between abnormal lung clearance of Tc-99m-DTPA and abnormal pulmonary uptake of Ga-67. This suggests that lung clearance of Tc-99m-DTPA may be used as a means for assessing disease activity in pulmonary sarcoidosis.