RESPIRATORY CLEARANCE OF TC-99M-DTPA AND PULMONARY INVOLVEMENT IN SARCOIDOSIS

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Abstract
To investigate the relationships between the respiratory epithelial clearance of micronic aerosolized 99mTc-DTPA (RC-DTPA) and pulmonary function, serum angiotensin-converting enzyme (SACE), and lymphocytic alveolitis in patients with sarcoidosis, RC-DTPA was measured in 49 non-smokers with pulmonary sarcoidosis and 38 normal nonsmokers. Pulmonary involvement was evaluated on chest roentgenograms (type O = normal, type I = hilar adenopathies, type II = hilar adenopathies associated with parenchymal shadows, type III = parenchymal shadows without adenopathy) and by pulmonary function tests. Serum angiotensin-converting enzyme was determined, and a bronchoalveolar lavage was performed for alveolar lymphocyte differential counting (Ly%), RC-DTPA was increased (.gtoreq. 1.96%/min) in 12 of 31 patients with type II or III involvement but was normal in all 18 patients with type 0 or I involvement (p = 0.002). Patients with increased RC-DTPA had low FVC, TLC, FEV1, and resting PaO2 (p < 0.05); resting and exercise AaPO2 were increased (p < 0.05), but RC-DTPA correlated negatively with FEV1 (p < 0.01), PaO2 at rest (p < 0.005), and DLCO (p < 0.05) and positively with resting and exercise AaPO2 (p < 0.01). In patients with increased RC-DTPA (42 .+-. 17%), Ly% did not differ from Ly% in patients with normal RC-DTPA (34 .+-. 16%). SACE was increased in patients with increased RC-DTPA (56 .+-. 26 U/ml versus 38 .+-. 16 U/ml; p = 0.007) and correlated positively with RC-DTPA (p < 0.001). We conclude that in patients with pulmonary sarcoidosis: (1) when RC-DTPA is increased, there is pulmonary parenchymal involvement on chest roentgenogram, impaired lung function, and increased SACE; (2) SACE increases in proportion to RC-DTPA; (3) increase in Rc-DTPA is not related to luminal lymphocytic alveolitis.

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