Blood leukocyte levels as potential prognostic markers in IPF

Background: The prognosis of IPF is poor and there is a need for clinically accessible prognostic biomarkers. Objective: To explore association between blood leukocytes (monocytes, neutrophils and lymphocytes) and prognosis in patients with IPF. Method: We performed a retrospective analysis of an IPF cohort (n=182) first seen in the Oxford ILD Service between 2013-2017. Correlation between full blood count within 4 months of first clinic and lung function decline, hospitalisation and survival was assessed using Cox Proportional Hazard regression analysis. Results: 128 patients had contemporaneous full blood count measurement within 4 months of first clinic assessment. Mean (±SD) length of follow up was 2.9 ±1.4y, age 75.2 ±7.8y, 78% male. Maximal time to censoring was 7.1 years. 25 (19.5%) cases had a hospitalisation event, 50 (43.9%) showed FVC decline >10%/y and death occurred in 56 (43.8%) cases. In multivariate models (adjusted for age, gender, initial FVC%) neutrophils were associated with FVC decline [HR 1.36, 95% CI 1.11-1.68, p=0.004] and all-cause mortality [1.24, 1.08-1.42, p=0.002]. Monocyte levels were associated with mortality only [1.36, 1.04-1.77, p=0.024]. In univariate modelling neutrophils were associated with hospitalisation [1.15, 1.0-1.32, p=0.049]. Dichotomised blood leukocytes levels (by mean) identified neutrophils >5.5x10³/µl as a correlate of all-cause mortality [2.3, 1.34-3.9, p=0.002]; median survival 36.2 vs 55 months. Conclusion: In this IPF cohort, raised neutrophil and monocyte levels are associated with greater lung function decline and increased risk of mortality over a 3 year period. Blood monocyte and neutrophil levels at time of initial assessment may serve as a prognostic biomarker.