Op0252 One-Year Trajectories of Diffusion Capacity of Carbon Monoxide as Potential Markers of Outcome in Systemic Sclerosis Associated Pulmonary Hypertension

Background: Preliminary data indicate that COMPERA 2.0 may be the most accurate tool for risk stratification in systemic sclerosis (SSc)-associated pulmonary arterial hypertension (PAH). Additionally, we have discovered that adding data on diffusion capacity of carbon monoxide (DLCO) to the risk assessment may improve accuracy. To be suitable for risk stratification, DLCO should display sensitivity to change at individual level and have an impact on mortality. Whether DLCO fulfills these criteria are to date unknown. Objectives: This study aims to evaluate relative and absolute changes in DLCO during 12 months from PAH diagnosis and their impact on mortality. Methods: We included SSc patients at Oslo University Hospital who underwent a right heart catheterization (RHC) between 2005 and 2020. 1.All patients fulfilled the new PAH criteria (mean pulmonary arterial pressure >20 mmHg, pulmonary artery wedge pressure ≤15 mmHg and pulmonary vascular resistance >2 WU). 2.All patients had available DLCO% predicted at time of PAH-diagnosis (±3 months) and after 12 months (±3 months). An improvement in DLCO was defined as an increase in DLCO% predicted of ≥5%. A worsening was defined as a decrease in DLCO% predicted of >5% and stable DLCO was considered a change of±5%. The use of upfront PAH-therapy was registered. We constructed Kaplan-Meier curves for mortality analysis. Results: Out of 106 patients diagnosed with PAH, 54 (51%) had a DLCO% predicted measurement available both at the time of diagnosis and after 12 months (Table 1). We identified 10 (19%) patients with DLCO improvement, 17 (32%) with worsening, and 27 (50%) with stable DLCO. Over a mean observation period of 98 months, 53 (56%) patients died, with a trend towards better survival in patients with improvement in DLCO (Figure 1). 5 (50%) died in the improved DLCO group, 10 (59%) in the worsened group and 12 (44%) in the DLCO stable group. Conclusion: We show that DLCO is sensitive to change in SSc patients with PAH. There was a trend towards better survival in patients who did not deteriorate in DLCO during the first year after PAH diagnosis. This supports our findings that DLCO should be taken into account in the risk stratification of SSc-PAH patients at the time of PAH diagnosis. REFERENCES: NIL. Acknowledgements: NIL. Disclosure of Interests: Håvard Fretheim Boehringer Ingelheim, Hilde Jenssen Bjørkekjær: None declared, Øyvind Midtvedt: None declared, Thao Nguyen: None declared, Hu Yi: None declared, Arne Andreassen Janssen, Janssen, Michael T Durheim Pfizer and AstraZeneca, Roche and Boehringer Ingelheim, Phuong Phuong Diep Boehringer-Ingelheim., Boehringer-Ingelheim., Torhild Garen: None declared, Øyvind Molberg: None declared, Anna-Maria Hoffmann-Vold Boehringer Ingelheim, Boehringer Ingelheim, Janssen, Medscape, Merck Sharp & Dohme, Novartis and Roche, ARXX, BMS, Boehringer Ingelheim, Genentech, Janssen, Medscape, Merck Sharp & Dohme and Roche, Boehringer Ingelheim, Janssen.