# Frequency and determinants of use of immunosuppressants in the Australian Scleroderma Cohort Study

## TL;DR

This study examines how often immunosuppressants are used in people with scleroderma in Australia and finds that their use is influenced by disease severity and has changed over time.

## Contribution

The study provides real-world insights into prescribing patterns and determinants of immunosuppressant use in systemic sclerosis over a 17-year period.

## Key findings

- Immunosuppressants were used by 60% of participants, with higher use in those with diffuse systemic sclerosis.
- Disease-modifying anti-rheumatic drug use increased over time, while prednisolone use decreased.
- Interstitial lung disease, synovitis, and myositis were key factors associated with immunosuppressant use.

## Abstract

To assess the frequency and determinants of immunosuppressant medication use in systemic sclerosis and changes in prescribing patterns over time.

The Australian Scleroderma Cohort Study participants meeting the American College of Rheumatology/European Alliance of Associations for Rheumatology criteria for systemic sclerosis with recorded treatment data were included. The Chi-square, two-sample t-tests or Wilcoxon rank-sum tests were used for between-group comparison as appropriate. Multivariable logistic regression models were used to establish the determinants of the use of immunosuppressants.

Of 2019 participants, 60% received immunosuppressants, including 81% of those with diffuse systemic sclerosis and 52% of those with limited systemic sclerosis (p < 0.001). Forty-six percent of patients received prednisolone and 40% disease-modifying anti-rheumatic drugs. Immunosuppressant use was more common in those with severe or inflammatory systemic sclerosis features, including interstitial lung disease, synovitis or myositis. Comparing prescribing patterns early in incident systemic sclerosis from 2007–2014 to 2015–2024, disease-modifying anti-rheumatic drug use increased (35% vs 56%, p < 0.001), while prednisolone use decreased (24% vs 17%, p = 0.046). Immunosuppressants were commenced earlier in incident systemic sclerosis in 2015–2024 versus 2007–2014 (1.8 (interquartile range = 1.0–3.2) vs 2.4 (interquartile range = 1.2–4.0) years, p = 0.011). In multivariable modelling, prednisolone use was associated with diffuse systemic sclerosis (odds ratio = 1.8, 95% confidence interval = 1.4–2.2, p < 0.001), interstitial lung disease (odds ratio = 2.1, 95% confidence interval = 1.7–2.5, p < 0.001), myositis (odds ratio = 2.7, 95% confidence interval = 1.8–4.0, p < 0.001), synovitis (odds ratio = 2.2, 95% confidence interval = 1.8–2.6, p < 0.001) and systemic sclerosis heart involvement (odds ratio = 1.4, 95% confidence interval = 1.0–2.0, p = 0.044). Disease-modifying anti-rheumatic drug exposure was associated with diffuse systemic sclerosis (odds ratio = 2.7, 95% confidence interval = 2.1–3.4, p < 0.001), interstitial lung disease (odds ratio = 2.2, 95% confidence interval = 1.7–2.7, p < 0.001), myositis (odds ratio = 3.6, 95% confidence interval = 2.4–5.5, p < 0.001) and synovitis (odds ratio = 4.2, 95% confidence interval = 3.5–5.2, p < 0.001) and inversely associated with age (odds ratio = 0.7, 95% confidence interval = 0.5–0.8, p < 0.01) and pulmonary arterial hypertension (odds ratio = 0.5, 95% confidence interval = 0.4–0.7, p < 0.001). In subgroups with diffuse systemic sclerosis and limited systemic sclerosis and different autoantibody profiles, findings were generally similar, with interstitial lung disease, synovitis and myositis tending to be associated with prednisolone and/or disease-modifying anti-rheumatic drug use, as was systemic sclerosis heart involvement in diffuse systemic sclerosis (p = 0.038).

Immunosuppressant use is common in systemic sclerosis, with broadly similar determinants of usage among subtypes and autoantibody status. These real-world data suggest that disease-modifying anti-rheumatic drug use has increased, with earlier implementation of treatment, and a reduction in use of glucocorticoids.