The association between white blood cell count and outcomes in patients with idiopathic pulmonary fibrosis.

BACKGROUND:The course of idiopathic pulmonary fibrosis (IPF) is uncertain with variable patterns of disease progression. We sought to evaluate the prognostic utility of the WBC, a routinely performed lab test, in a well-defined cohort of outpatient IPF subjects. METHODS:We reviewed IPF patient records from two independent ILD centers (Inova Fairfax in Falls Church, VA, USA and Ege University Hospital in Izmir, Turkey) between 2007 and 2018. Demographics, CBC data, and patient outcomes were obtained. Survival differences were analyzed. RESULTS:There were 436 IPF outpatients in the cohort with a median WBC of 8.9 × 109 cells per liter. For pragmatic purposes, patients were categorized into two groups, WBC ≥9 or WBC <9. Patients with WBC <9 had a median transplant-free survival of 50.5 months from the time of the CBC, compared to 32.4 months for those with WBC ≥9 (p < 0.0001). The association between WBC and attenuated survival remained significant after adjusting for GAP stage, steroid use, and antifibrotic use when WBC was analyzed both as a continuous (HR: 1.11; 95% CI: 1.05-1.17) and a dichotomized variable (high (WBC ≥9) vs. low (WBC <9), (HR: 1.53; 95% CI:1.09-2.15). WBC and absolute neutrophil count (ANC) were highly correlated suggesting that PMNs account for most of this association (r = 0.92). CONCLUSIONS:Baseline WBC may impart important and readily available prognostic information in outpatients with IPF. Further studies are warranted to validate this as a potential biomarker for IPF, as well as to define the biologic basis for the association.