Monocytes and neutrophil levels are potentially linked to progression to IPF for patients with indeterminate UIP CT pattern.

RationaleIdiopathic pulmonary fibrosis (IPF) is a progressive fibrotic lung disease with poor prognosis. Identifying patients early may allow intervention which could limit progression. The indeterminate for UIP (iUIP) CT pattern, defined in the 2018 IPF guidelines, could be a precursor to IPF but there is limited data on how patients with iUIP progress over time. ObjectiveTo evaluate the radiological progression of iUIP and explore factors linked to progression to IPF. MethodsWe performed a retrospective analysis of a lung fibrosis clinic cohort (n=230) seen between 2013-2017. Cases with iUIP were identified; first ever CTs for each patient found and categorised as non-progressor or progressors (the latter defined as increase in extent of disease or to definite or probable UIP CT pattern) during their follow up. Lung function trends, haematological data and patient demographics were examined to explore disease evolution and potential contribution to progression. Results48 cases with iUIP CT pattern were identified. Of these, 32 had follow up CT scans, of which 23 demonstrated progression. 17 patients in this cohort were diagnosed with IPF over a mean (S.D.) period of 3.9 ({+/-}1.9) years. Monocyte [HR 23, CI 1.6-340, p=0.03] and neutrophil levels [HR 1.8, CI 1.3-2.3, p<0.001] obtained around the time of initial CT, were associated with progression to IPF using Cox proportional hazard modelling. Conclusion53% of our evaluable iUIP patients progressed to IPF over a mean of four years. Monocyte and neutrophil levels at initial CT were significantly associated with progression in disease. These data provide a single-centre analysis of the evolution of patients with iUIP CT pattern, and first signal for potential factors associated with progression to IPF. Key messageO_ST_ABSWhat is the key question?C_ST_ABSHow does the indeterminate for UIP (iUIP) interstitial CT pattern evolve over time and what factors are associated with progression to definite and probable UIP pattern. What is the bottom line?In this retrospective single centre analysis, 53% of evaluable cases with iUIP on initial CT scan progressed to probable or definite UIP CT pattern over an average of 4 years. Monocyte and neutrophil levels performed around the time of initial CT were significantly associated with progression to definite and probable UIP pattern. Why read on?We discuss the implications of these findings, its strengths and limitations.