Total lung capacity is predictive of disease severity and survival in systemic sclerosis: A longitudinal analysis in 2347 patients from the French National Cohort Study.

Background: Total lung capacity (TLC) is seldom assessed in the prediction of systemic sclerosis (SSc) disease severity.

Objective: To describe and analyse TLC in SSc.

Methods: We performed a retrospective multicentre study of SSc patients enrolled in the French national SSc cohort with at least one TLC assessment, described patients based on baseline TLC measurements, modelized TLC trajectories in SSc, and associated TLC measures with disease prognosis.

Results: Two thousand three hundred and forty-seven patients were included in the study. Baseline TLC was associated with disease severity and survival, as well as with the occurrence of interstitial lung disease (ILD), lung fibrosis (LF), and pulmonary arterial hypertension (PAH). Individual TLC trajectories varied among patients. Different models of TLC trajectories were assessed using latent process mixed models. The best model showed that the vast majority of SSc patients had stable TLC trajectories and clustered patients into three groups predictive of SSc survival, ILD, LF, and PAH. Lastly, a 10 % decrease of TLC was found to be predictive of a 5 % decrease in forced vital capacity (FVC), a 10 % decrease in DLCO, and consequently an earlier predictive marker of ILD and LF than FVC.

Limitations: Retrospective study.

Conclusion: TLC is predictive of disease severity and survival in SSc and SSc-ILD. This work suggests TLC as an earlier risk factor for ILD and LF than FVC in SSc.