Predictive biomarkers of persistent interstitial changes after COVID19

<bold>Introduction:</bold>Post-covid pulmonary sequelae have become a health problem. Although interstitial lung alterations usually improve, they may persist after a year from the infection. Predicting if the patient will improve or not, would optimize the follow-up. <bold>Objective:</bold>Determine the utility of biomarkers as predictors of persistent covid19 interstitial changes <bold>Methods:</bold>Observational, prospective, multicenter study of patients with severe covid19 pneumonia(IRCU and/or ICU) from June to December 2020. Patients were included consecutively and visits made at 3,6 and 12 months. Symptoms were recorded(SL12 questionnaire);Chest-CT and 6mWT at 1 and 12 months;PFTs at 2,6 and 12 months;blood samples at 3 and 12 months. Patients were characterized according to interstitial changes at 3 months:0-normalization vs 1-interstitial persistence;and at 12 months:0-normalization;1-1 persistent interstitial changes;1-2 subtle changes. The analyzed serum proinflammatory(IL-8,IL-6,TNF-alpha) and profibrotic(MMPs,TIMPs,KL-6,PAI-1,VEGF) mediators were correlated with this clinical characterization. <bold>Results:</bold>361 patients were included:23% resolved infiltrates at 3 months. At 12 months, 48% had a normal chest-CT, 20% showed minimal changes and 32% persisted with significant radiological changes. Days of admission, IMV or NIMV, HFNC,tracheostomy, pulmonary embolism, and post-ARDS pulmonary fibrosis were associated with persistent interstitial changes at 12 months. Of the analyzed biomarkers, MMP7 and KL6 were significantly higher in patients with interstitial changes at both short and long term(3 and 12 months) <bold>Conclusion:</bold>Inflammatory biomarkers such as KL6 could help define which patients will persist with long term postcovid interstitial changes