Impact Of Bal Lymphocytosis > 15% On The Prognosis Of Chronic Idiopathic Interstitial Pneumonias Other Than Idiopathic Pulmonary Fibrosis: A Retrospective Nationwide Study Based On Multidisciplinary Discussion

Background: Impact of bronchoalveolar lavage (BAL) lymphocytosis >15% on the prognosis of chronic idiopathic interstitial pneumonias other than idiopathic pulmonary fibrosis (non-IPF) has never been evaluated. Methods: Japanese chronic non-IPF patients treated with corticosteroids were identified using the nationwide registry along with multidisciplinary discussion (MDD). We compared the clinical, radiological and pathological features, and outcomes between patients with BAL lymphocytosis >15% and those with BAL lymphocytes ≤15%. Results: Of the 110 patients with chronic non-IPF, 47 (42.7%) had BAL lymphocytosis >15%. The most prevalent MDD diagnosis was unclassifiable IIPs (64.5%), followed by iNSIP (22.7%). Immunosuppressants were administered in 69 (62.7%) patients. There were no significant difference in HRCT and pathological patterns, MDD diagnoses, and treatment regimens between the two groups. One-year changes in KL-6 and FVC % predicted were significantly better in patients with BAL lymphocytosis >15% than those with BAL lymphocytes ≤15%. Patients with BAL lymphocytosis >15% had longer OS than those with BAL lymphocytes ≤15% (Log-rank test, p =0.019). In multivariate analysis, BAL lymphocytosis >15% was a significant prognostic factor for overall survival (HR: 0.37; 95% CI, 0.16-0.87; p =0.022), in addition to FVC % predicted and interstitial pneumonia with autoimmune features. Conclusions: BAL lymphocytosis >15% is associated with favorable outcome in chronic non-IPF. Evaluation of BAL lymphocytes would be helpful to identify corticosteroid-effective patients.