Blood neutrophil levels in IPF patients are significantly associated with quantitative radiological progression

Abstract

Background: There is a need for a simple blood measurement to identify IPF patients at risk of disease progression.

Objective: Determine if blood leukocyte levels are associated with progression of fibrosis in IPF using automated CT Lung texture analysis (CALIPER).

Methods: In an Oxford IPF cohort (n=164) we determined correlation between blood leukocytes (<4 months from 1st CT) and baseline CALIPER total lung fibrosis (TLF) score, pulmonary vessel volume (PVV), FVC% and TLCO%. Leukocyte (monocytes, neutrophil and lymphocytes) association with the outcomes of increase in fibrosis >10% / litre and FVC decline >10% between CTs was analysed (Cox Regression).

Results: Mean age of cohort 75.1 SD± 7.9y, 90% male, FVC 76.6% (66.6-91.2), TLCO 56.9% (49.5-67.0). Neutrophil level correlated with TLF (Pearson r=0.208, p=0.007) and PVV (r=0.259, p=0.001). There was significant correlation between neutrophils and upper and middle zone fibrosis and PVV, but weaker correlation with FVC% (r=-0.127, p=0.029) and TLCO% (r=-0.104, p=0.079). 71 cases had repeat CT; mean time 28.9m (±16.7) between CTs. In multivariate analysis of age, gender, baseline FVC, % change in CALIPER lung volume and leukocyte levels, neutrophil levels [HR 1.93, 95%CI 1.14-3.26, p=0.015] and reduction in lung volume [HR 0.86, 0.79-0.93, p<0.001] were significantly associated with progression of TLF, but not with FVC decline [HR 1.17, 0.91-1.52, p=0.222].

Conclusion: In our cohort, neutrophil levels showed strongest correlation with amount of fibrosis and PVV, and radiological progression of fibrosis between CTs (within 3 years). Neutrophil levels could indicate patients at greater risk of progression of fibrosis in IPF.