Comprehensive assessment of complete blood count as a prognostic biomarker in interstitial lung diseases.

BACKGROUND: While prognostic changes in complete blood count (CBC) parameters, such as elevated monocytes and neutrophils, have been studied in idiopathic pulmonary fibrosis (IPF), they are less well characterized in other interstitial lung diseases (ILD). We aimed to comprehensively assess the prognostic value of CBC parameters in various ILDs. METHODS: This retrospective derivation-validation registry-based study included consecutive ILD patients followed-up at tertiary referral centers that had available CBC and follow-up information. Optimal prognostic CBC cutoffs were determined using Youden's index. Adjusted multivariate Cox regression analyses were used to assess the relation between CBC components and a composite outcome of lung transplantation or death of any cause. RESULTS: The derivation cohort included 369 patients (50.7% males, median age 67, 82.7% non-IPF) with a median follow-up of 20 months. Neutrophil counts >5.6 K/μL and platelets <149 K/μL were associated with worse outcome, although only neutrophil counts were independent predictors. The independent validation cohort of 696 patients (53.9% males, median age 66, 67.1% non-IPF) followed for 60 months, confirmed the prognostic value of neutrophils and platelets in ILD, employing the same cutoffs. In a subgroup analysis, neutrophil counts >5.6 K/μL were prognostic across most ILD categories except in connective tissue diseases (CTD), in both the derivation and validation cohorts. CONCLUSION: A neutrophil count exceeding 5.6 K/μL at the time of ILD diagnosis was validated as an independent biomarker of poor outcomes in ILD, with the exception of CTD-ILD. Additionally, a platelet count below 149 K/μL demonstrated prognostic significance.