RED CELL DISTRIBUTION WIDTH (RDW) AND NEUTROPHIL LYMPHOCYTE RATIO (NLR) AS PROGNOSTIC MARKERS IN IDIOPATHIC PULMONARY FIBROSIS (IPF)

Introduction and Objectives Idiopathic Pulmonary Fibrosis (IPF) has a median survival of ~ 2–3 years, but there is significant variability and hence difficulty in advising patients at a personal level. The full blood count (FBC) is readily accessible and gives a Red Cell Distribution Width (RDW), which describes the percentage variation in red cell size. The neutrophil and lymphocyte count can be used to calculate a ratio (NLR). Limited published work has evaluated the prognostic significance of these markers in IPF. Our aim was to assess longitudinal changes in RDW and NLR as potential prognosticators in IPF. Methods Patients with IPF were identified from the Royal Devon and Exeter Hospital (2005–2019). Data collected: baseline characteristics, survival, PFTs and FBC <6 months from diagnosis and 6–18 months during follow-up. Patients with insufficient data were excluded. Blood parameters were stratified into quartiles for subsequent Kaplan-Meier survival analyses, Mann-Whitney U-test and Spearman’s rank correlation. Results 131 patients were included in analysis. Median change/month for NLR (deltaNLR) and RDW (deltaRDW) were 0.17 and 0.02 respectively, indicating minimal longitudinal variation. Anti-fibrotic treatment did not modify deltaRDW or deltaNLR. However, stratifying by median deltaRDW significantly impacted on survival (median 33 months with deltaRDW>0.02 vs 59 months; P = 0.04). Median survival stratified on baseline RDW was 35 months (highest quartile) vs 47 months (1st-3rd quartiles) although this did not reach significance (P =0.1439). Median survival based on follow-up RDW was 25 months (highest quartile) vs 59 months (1st-3rd quartiles; P=0.0021) and this was negatively correlated with FVC (P=0.0056). Both baseline and follow-up NLR had significantly shorter median survival in the highest quartile (28 months; p<0.05) compared with 47 months (baseline 1st-3rd quartile) or 59 months (follow-up 1st-3rd quartile). FVC was negatively correlated to baseline NLR (P=0.0282). Conclusions RDW and NLR demonstrated significant relationships with survival and correlations with FVC. Increasing RDW resulted in poorer outcomes. Although limited by the small retrospective cohort, this data indicates that readily available FBC may have utility in prognostication and progression monitoring in IPF, independent of antifibrotic treatment. RDW may be confounded by co-morbidities; further work to assess this is warranted.