Monocyte Count as a Prognostic Biomarker in Patients with Idiopathic Pulmonary Fibrosis

Abstract Rationale There is an urgent need for simple, cost-effective prognostic biomarkers for idiopathic pulmonary fibrosis (IPF); biomarkers that show potential include monocyte count. Objectives We used pooled data from pirfenidone and IFNγ-1b trials to explore the association between monocyte count and prognosis in patients with IPF. Methods This retrospective pooled analysis included patients (active and placebo arms) from the following four phase III, randomized, placebo-controlled trials: ASCEND (NCT01366209), CAPACITY (NCT00287729 and NCT00287716), and INSPIRE (NCT00075998). Outcomes included IPF progression (≥10% absolute decline in FVC% predicted, ≥50 m decline in 6-minute-walk distance, or death), all-cause hospitalization, and all-cause mortality over 1 year. The relationship between monocyte count (defined as time-dependent) and outcomes was assessed using bivariate and multivariable models. Measurements and Main Results This analysis included 2,067 patients stratified by monocyte count (at baseline: 0.60 × 109cells/L n = 1,609, 0.60 to 0.95 × 109cells/L n = 408, and ≥0.95 × 109cells/L n = 50). In adjusted analyses, a higher proportion of patients with monocyte counts of 0.60 to 0.95 × 109cells/L or ≥0.95 × 109cells/L versus 0.60 × 109cells/L experienced IPF progression (P = 0.016 and P = 0.002, respectively), all-cause hospitalization (P = 0.030 and P = 0.003, respectively), and all-cause mortality (P = 0.005 and P 0.001, respectively) over 1 year. Change in monocyte count from baseline was not associated with any of the outcomes over 1 year and did not appear to be affected by study treatment. Conclusions In patients with IPF, elevated monocyte count was associated with increased risks of IPF progression, hospitalization, and mortality. Monocyte count may provide a simple and inexpensive prognostic biomarker in IPF.