Disease frequency, patient characteristics, comorbidity outcomes and immunosuppressive therapy in systemic sclerosis and systemic sclerosis-associated interstitial lung disease: a US cohort study.

OBJECTIVES

To investigate prevalence estimates and incidence rates (IRs) for SSc and SSc-associated interstitial lung disease (SSc-ILD) cohorts and describe patient characteristics, immunosuppressive therapy (IST) and comorbid outcomes among incident SSc and SSc-ILD cohorts.

METHODS

Data were obtained from the US IBM MarketScan (2008-2017) claims database using algorithms developed with expert consultation. For the SSc cohort, newly diagnosed patients (aged ≥18 years) had one or more diagnostic claim for SSc. For the SSc-ILD cohort, patients had an additional ILD claim. Sensitivity analyses using two or more claims or alternative ILD diagnostic codes were also conducted.

RESULTS

When requiring one or more diagnostic claim, the prevalence of SSc and SSc-ILD per 100 000 persons was 72.1 and 19.0. The IR for SSc and SSc-ILD per 100 000 person-years was 18.3 and 4.3. Sensitivity analyses requiring two or more claims yielded much lower prevalence (SSc: 41.5; SSc-ILD: 13.3) and IR (SSc: 8.8; SSc-ILD: 1.6) estimates. Patients with SSc-ILD were older, with increased comorbidities and diagnostic procedures at baseline. MTX and MMF were the most common ISTs; 12.7% of the SSc-ILD cohort received therapy at baseline vs 8.2% for SSc. A total of 42.5% and 45.0% of the SSc and SSc-ILD cohorts, respectively, started a stable IST regimen and 21.7% and 19.4% of these had an escalation. Skin disorders were the most common comorbid outcome in both cohorts during follow-up.

CONCLUSIONS

SSc, with or without associated ILD, is a rare disease in the US. Newly diagnosed patients with SSc-ILD had received more IST and had more comorbidities compared with newly diagnosed SSc.