The role of serum and bronchoalveolar lavage fluid chitotriosidase activity on diagnosis, disease characteristics and prognosis of sarcoidosis

Introduction: Sarcoidosis is a multisystem granulomatous disease with an unpredictable clinical course. Chitotriosidase is a chitinase mainly expressed by activated macrophages. Increased chitotriosidase activity has been reported in serum and bronchoalveolar lavage (BAL) of sarcoidosis patients compared to healthy controls. This study aims to evaluate the role of serum and BAL chitotriosidase activity on diagnosis, disease characteristics, and prognosis of sarcoidosis. Materials and Methods: Patients referred with suspected sarcoidosis or other interstitial lung disease were prospectively included in the study. All patients underwent bronchoscopy with BAL. Serum and BAL chitotriosidase activity, BAL differential cell counts, and lymphocyte phenotypes were determined. Sarcoidosis patients were followed up regularly. Results: Forty-two sarcoidosis and 28 non-sarcoidosis patients were included in the study. Serum chitotriosidase activity was higher in sarcoidosis group 247.5 (2.78-461) vs 108 (2.78-272) nmol/h/mL (p< 0.001). BAL chitotriosidase activity tended to be higher in sarcoidosis group 11 (2-308) vs 6.95 (2.27-44) nmol/h/mg but was not found to be statistically significant (p= 0.11). Serum and BAL chitotriosidase activities were correlated with each other (p= 0.023, r= 0.355). No significant difference was found between the diagnostic performance of BAL CD4/CD8 ratio and serum chitotriosidase activity (p= 0.079). Serum chitotriosidase and ACE activities were correlated with each other (p= 0.004, r= 0.457). No significant difference was found between serum or BAL chitotriosidase activity and stage or extrapulmonary involvement. Serum chitotriosidase activity was higher in patients who needed systemic therapy at diagnosis (p= 0.046). However, no significant difference was found between serum or BAL chitotriosidase activities and disease progression (p= 0.395 and p= 0.723, respectively). Conclusion: Serum chitotriosidase activity can be helpful in the differential diagnosis of sarcoidosis with a similar diagnostic performance with BAL CD4/CD8 ratio. Although serum chitotriosidase activity at diagnosis does not predict progressive disease, it is associated with the need for systemic therapy at diagnosis. Serial chitotriosidase measurements may be useful in monitoring disease progression during follow-up