Background: As SSc-ILD can develop progressive pulmonary fibrosis, close monitorization of pulmonary function in these patients is crucial.

Aim: To describe the evolution over time of pulmonary functional tests (PFT) results in patients with SSc-ILD.

Subjects and method: SSc patients with serial PFT. Change over time was defined by 2 methods: (1): a relative decline in FVC???10% or a relative decline in DLCO???15% (Cottin V et al 2018) and (2):an absolute decline in FVC???5% or absolute decline in DLCO???10% (Raghu G et al 2022). The lung function decline was first described in 2018 and these patients were followed until 2022.

Results: Among 31 patients with SSc who performed PFTs during the year 2018 in our department, 20 patients (17 females, mean age 53,2) had been prior tested at least once in the past; mean period of follow-up was 39,7 months (range 3-84); mean FVC 2,87L - 91,8%, mean DLCO 75,4%. Using the previous criteria (a relative decline in FVC???10% or a relative decline in DLCO???15%) we found that 6 patients worsened on FVC and 4 on DLCO. Using the new criteria for defining physiological evidence of disease progression (absolute decline in FVC???5% or absolute decline in DLCO???10%) we found another 2 cases (1 worsened in FVC and 1 in DLCO) in this group. Among the 20 patients 11 had a new PFT until 2023: only 6 out of the 9 patients that had a decline either on FVC, on DLCO or in both in 2018 were reevaluated ? 5 were stationary or improved and only 1 worsened.

Conclusion. We found no important differences between two methods of defining physiological evidence of disease progression in SSc-ILD. Close follow up is useful in adjusting the treatment and can prevent further functional degradation.