A Comparison of Pulmonary Function Test (PFT) Trajectories in Idiopathic Pulmonary Fibrosis (IPF) and Combined Pulmonary Fibrosis and Emphysema (CPFE) Syndrome

<bold>Background:</bold> Coexistent emphysema and usual interstitial pneumonia (UIP) on CT is increasingly recognised. It is unclear if CPFE is a distinct clinical entity compared to IPF. <bold>Aim:</bold> To compare PFT parameter trajectories of patients with IPF and CPFE. <bold>Methods:</bold> A retrospective cohort study of CPFE (n = 114) and IPF (n = 332) between 2009-2020 at 4 UK NHS sites. Demographic and clinical data were extracted from electronic medical records, with patients grouped from CT reports as IPF or CPFE. Baseline demographics are presented as mean ±SD and compared using t-tests or X². Annual decline in PFTs (slope) were calculated for those with ≥3 measurements. Multivariable analysis for FVC slope was performed, with adjustment for baseline age, FVC % predicted (FVCpp) and smoking status. <bold>Results:</bold> Those with IPF had a similar age (72.7± 9.02 vs 72.4 ±9.36, p=0.732) and proportion of males (69.3% vs 65.1%, p=0.478) compared to CPFE. FVCpp was lower at baseline for IPF compared to CPFE (80.2%±18.1 vs 85.7± 17.6 respectively, p=0.005). <italic>Table 1</italic> shows unadjusted slopes for FEV1 and FVC. In multivariable analysis, IPF was associated with a higher rate of FVC decline vs CPFE (−94.3 mL/year, 95% CI -156.6 to -32.0, p=0.003). <table-wrap><object-id>erj;64/suppl_68/PA1558/TB1</object-id><object-id>T1</object-id><object-id>TB1</object-id><table><colgroup><col></col><col></col><col></col><col></col></colgroup><tbody><tr><td></td><td>IPF group (n=332)</td><td>CPFE group (n=114)</td><td>P-value</td></tr><tr><td>FEV1 mL/ year change (unadjusted)</td><td>-122.4 ±169.5</td><td>-49.48 ±165.4</td><td><0.001</td></tr><tr><td>FVC mL/ year change (unadjusted)</td><td>-164.7 ±222.17</td><td>-79.39 ±326.7</td><td>0.005</td></tr></tbody></table></table-wrap> <bold>Discussion:</bold> FVC is preserved both at baseline and longitudinally in CPFE compared with IPF and is therefore not an accurate marker of disease progression in CPFE. Gas transfer measures may be a better marker of progression, with analyses ongoing.