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Introduction Idiopathic pulmonary fibrosis (IPF) is characterised by progressive lung function decline and poor survival. In England, NICE recommends antifibrotic therapy based on FVC % predicted thresholds. Introduction of race-neutral GLI-2022 reference equations may alter spirometry-derived eligibility for antifibrotic therapy, but their impact on eligibility classification in IPF patients remains unclear.Aims To compare FVC derived NICE antifibrotic eligibility at baseline and at 12 months using GLI-2012 versus GLI-2022 reference equations, including eligibility for nintedanib (FVC ≥50%), pirfenidone (FVC 50–80%), and modelled to continuation criteria (FVC <50% or ≥10 percentage-point absolute decline).Methods Retrospective data was analysised in IPF patients (2019–2024). FVC predicted values were calculated using GLI-2012 and GLI-2022 reference equations. Differences in FVC % predicted were assessed using paired t-tests, and changes in eligibility classification were analysed using McNemar’s test.Results The cohort included 467 IPF patients (mean age 74 ± 8 years; 76% male). Mean baseline FVC % predicted was higher using GLI-2022 than GLI-2012 (77.5 ± 14.2 vs 74.3 ± 14.2; p<0.001). Comparing GLI-2012 vs 2022 the ≥50% threshold, eligibility increased from 97.2% to 98.3%, with five patients reclassified as eligible (McNemar p=0.025). Fewer patients met the 50–80% pirfenidone threshold under GLI-2022 compared with GLI-2012 (57.0% vs 66.8%; p<0.001), with 47 reclassified above 80%. Among 209 patients with 12-month follow-up, FVC % predicted remained higher with GLI-2022 (73.8 ± 15.5 vs 70.9 ± 14.7; p<0.001). The proportion dropping below 50% at 12 months was similar (5.34% vs 4.85%; p>0.05). Although mean FVC% predicted decline differed slightly between equations (−3.68% ± 9.96% vs −3.38% ± 9.46%; p<0.001), 8.1% met the ≥10% absolute decline criterion.Conclusion Use of the GLI-2022 in place of of GLI-2012 reference equations resulted in modest but statistically significant reclassification of spirometry-derived antifibrotic eligibility, particularly reducing the proportion meeting pirfenidone thresholds. In contrast, GLI-2022 has minimal impact on modelled NICE progression criteria over 12 months. Adoption of updated reference equations may therefore influence access to antifibrotic therapy and should be considered when interpreting spirometry-based eligibility in IPF.