TY - JOUR T1 - Bronchoalveolar Lavage Fluid Lymphocytosis in Chronic Hypersensitivity Pneumonitis: A Systematic Review and Meta-Analysis JF - European Respiratory Journal JO - Eur Respir J DO - 10.1183/13993003.00206-2020 SP - 2000206 AU - Nicola Adderley AU - Christopher J. Humphreys AU - Hayley Barnes AU - Brett Ley AU - Zahra A. Premji AU - Kerri A. Johannson Y1 - 2020/01/01 UR - http://erj.ersjournals.com/content/early/2020/04/01/13993003.00206-2020.abstract N2 - Background The role of bronchoalveolar lavage fluid (BAL) lymphocyte% to diagnose chronic hypersensitivity pneumonitis (CHP) is unclear. We conducted a systematic review and meta-analysis of BAL lymphocyte% in the diagnosis of CHP.Methods We searched Medline, Embase and Cochrane library from inception to August 2019. Individual patient data were obtained to test performance characteristics of BAL lymphocyte% at different thresholds. Random-effects models were used for pooled estimates, with comparisons made between CHP and non-CHP interstitial lung diseases (ILD).Results Fifty-three studies were included in the systematic review and 42 in the meta-analysis. The pooled estimate for BAL lymphocyte% was 42.8% (95%CI 37.7–47.8, I2=95.3%) in CHP, 10.0% (95%CI 6.9–13.1, I2=91.2%) in idiopathic pulmonary fibrosis (IPF), 23.1% (95% CI 3.0–43.2, I2=85.2%) in non-IPF idiopathic interstitial pneumonia (IIP), 23.4% (95%CI 11.0–35.9, I2=45.7%) in connective-tissue disease ILD (CTD-ILD), and 31.2% (95% CI 17.6–44.8, I2=95.2%) in sarcoidosis. Results differed between CHP and IPF (p<0.0001), non-IPF IIP (p=0.0309), and CTD-ILD (p=0.0824), but not between sarcoidosis (p=0.0966). Using individual patient data from eight studies, lymphocyte% threshold >20% provided sensitivity of 68.1% and specificity of 64.8% for CHP. Higher thresholds provided lower sensitivity with higher specificity. Older age and ever having smoked were associated with lower lymphocyte% in CHP.Conclusions BAL lymphocyte% is higher in CHP compared to IPF and other IIP, with higher thresholds providing improved specificity at the cost of sensitivity. However, parent studies are at risk of incorporation bias, and prospective studies should evaluate the additive discriminate value of BAL lymphocyte% to accurately diagnose CHP.FootnotesThis manuscript has recently been accepted for publication in the European Respiratory Journal. It is published here in its accepted form prior to copyediting and typesetting by our production team. After these production processes are complete and the authors have approved the resulting proofs, the article will move to the latest issue of the ERJ online. Please open or download the PDF to view this article.Conflict of interest: Dr. Adderley has nothing to disclose.Conflict of interest: Dr. Humphreys has nothing to disclose.Conflict of interest: Dr. Barnes has nothing to disclose.Conflict of interest: Dr. Ley has nothing to disclose.Conflict of interest: Dr. Premji has nothing to disclose.Conflict of interest: Dr. Johannson reports personal fees and other from Boehringer-Ingelheim, personal fees and other from Hoffman La Roche Ltd, personal fees and other from Theravance, personal fees and other from Blade Therapeutics, grants from Chest Foundation, grants from University of Calgary School of Medicine, grants from Pulmonary Fibrosis Society of Calgary, grants from UCB Biopharma SPRL, outside the submitted work. ER -