High peripheral blood monocytes as a predictive factor of fibrotic ILD worsening

<bold>Background:</bold> Interstitial lung disease (ILD) is a heterogeneous group of different pathologies which can have an unpredictable course. This study aimed to determine the role of peripheral blood monocytes as a prognostic factor in ILD. <bold>Methods:</bold> Retrospective study including patients followed up for fibrotic ILD (confirmed by chest CT scan) at the Pulmonology Department of Mongi Slim Hospital, in Tunis-Tunisia, from January 2017 to January 2024. Patients were subdivided into 2 groups according to the course of ILD during follow up. G0: group with good evolution (stability or improvement) and G1: group with a worsening ILD. <bold>Results:</bold> A total of 108 patients were enrolled(mean age=68years, gender-ratio=0.9). Dyspnea(77.8%)and chronic cough(75%)were the most frequently reported complaints. On biology, average peripheral blood monocytes count was 578/mm3.ILD was classified as: sarcoidosis(n=31),IPF (n=13),idiopathic NSIP(n=13),SS-ILD (n=10),RA-ILD (n=9),HSP (n=7), RA-SS-ILD(n=3),IPAF (n=4),emphysema/fibrosis syndrome (n=3),myositis (n=5),scleroderma (n=2), granulomatosis with polyangiitis(n=2),ILD related to smoking(n=2),OP(n=1),pleuro-pulmonary fibroelastosis(n=1),silicosis (n=1),unclassifiable-ILD(n=1). Average values of PFT whereas the diagnosis of ILD was made, were:SpO2=94%,FVC=2.254l(59%),TLC=3.923l(65%),DLCO=44%. The course of ILD was towards worsening in 24.1% of patients. Univariate analysis revealed that significant predictive factors for ILD worsening were:high peripheral blood monocytes(479/mm3 for G0 vs 578/mm3 for G1 ; p=0.044) and FVC at the diagnosis of ILD(70% for G0 vs 59% for G1(p=0.053). <bold>Conclusion:</bold> Predictive factors for ILD worsening was high blood monocytes levels and impaired FVC at the diagnosis of ILD.