Peripheral white cell counts and mortality across different interstitial lung diseases

<bold>Introduction:</bold> The association between peripheral white cell counts (WCC) and survival in fibrotic Interstitial Lung Diseases (ILD) remains unclear. We explored this relationship across different ILDs. <bold>Methods:</bold> Patients with fibrotic hypersensitivity pneumonitis (fHP; N=302), idiopathic pulmonary fibrosis (IPF; N=621), rheumatoid arthritis associated ILD (RA-ILD; N=141), and systemic sclerosis associated ILD (SSc-ILD; N=122), presenting to our center between 2010-2019 with FBC measurements within 3 months of first lung function test were included. Multivariable cox proportional hazards analyses, including age, gender, smoking history, disease severity (Composite physiologic index; CPI), corticosteroid use and recent infection, were performed to assess associations with 5-year all-cause-mortality. In order to meet the proportional hazard assumption, an interaction term between CPI and time <1 years was added to the multivariable models. <bold>Results:</bold> On multivariable analysis, total WCC (HR (95%CI): 1.06 (1.00-1.12), p=0.049), monocyte (2.12(1.05–4.29), p=0.04), eosinophil (2.24 (1.15-4.34), p=0.02) counts and neutrophil-to-lymphocyte ratio (NLR) (1.02 (1.00-1.04), p=0.04) were associated with shorter survival in fHP. In IPF, higher neutrophil counts (1.05(1.00-1.09), p=0.03) and NLR (1.05 (1.02-1.09), p=0.002) were associated with shorter survival. Relationships in RA-ILD and SSc-ILD were not significant on multivariable analysis. <bold>Conclusion:</bold> Higher total WCC, monocyte, and eosinophil counts and NLR were independently associated with shorter survival in fHP, as were higher neutrophil count and NLR in IPF, suggesting their potential use as prognostic markers, if confirmed in further cohorts.