The ER for AECA in serum and BAL fluid did not correlate with pulmonary function, other serologic markers, or the findings on BAL. ER was not significantly correlated with data concerning disease activity, such as the percentage of lymphocytes, the CD4/CD8 ratio in BAL, and serum ACE levels. At the time of diagnosis, none of the patients had serious organ damage that needed systemic corticosteroid therapy. During the observation period, 12 patients deteriorated and needed systemic corticosteroid therapy for organ insufficiency: 7 patients for deterioration of pulmonary disease with progressive loss of lung function, 2 patients for visual impairment, 2 patients for cardiac sarcoidosis, and 1 patient for hypercalcemia and renal insufficiency. Compared with the ER in the 28 patients in whom the disease resolved spontaneously and who did not need corticosteroid therapy during the observation period (0.379 [IQR, 0.296 to 0.436] for serum; 0.184 [IQR, 0.122 to 0.327] for BAL fluid), the ER in these 12 patients (0.562 [IQR, 0.482 to 0.704] for serum; 0.405 [IQR, 0.234 to 0.756] for BAL fluid) was significantly higher in both serum and BAL fluid (p < 0.02 and p < 0.05, respectively). On analysis of dichotomization, among the 12 patients who deteriorated and needed systemic corticosteroid therapy for organ insufficiency, 7 patients had a positive ratio of serum AECA (sensitivity, 58.3%). Among the 28 patients who did not deteriorate, two had a positive ratio of AECA (specificity, 92.9%). In contrast, seven of the nine patients with elevated serum levels of AECA deteriorated and needed systemic corticosteroid therapy (positive predictive value, 77.8%). Compared with serum, the sensitivity and specificity of BAL fluid was low: 50.0% and 85.7%, respectively.