Development of a Composite Outcome Measure for Systemic Sclerosis Related Interstitial Lung Disease

Area of Science:

• Rheumatology
• Pulmonology
• Clinical Trials

Background:

• Systemic sclerosis-related interstitial lung disease (SSc-ILD) trials often rely on forced vital capacity (FVC) as the primary outcome.
• Combining multiple outcome measures may offer a more comprehensive assessment of treatment response and reduce Type I error risk.

Purpose of the Study:

• To develop and validate a composite outcome measure for assessing treatment response in SSc-ILD patients.
• To evaluate if a composite outcome provides a more robust measure of treatment efficacy compared to FVC alone.

Main Methods:

• Utilized data from the Scleroderma Lung Study I (SLS-I), a randomized controlled trial of cyclophosphamide (CYC) versus placebo in 158 SSc-ILD patients.
• Selected variables with significant treatment effects (p<0.05) including FVC% predicted, quantitative lung fibrosis (QLF-ZM), transitional dyspnea index (TDI), and Health Assessment Questionnaire-Disability Index (HAQ-DI).
• Employed principal component analysis (PCA) to create a composite outcome measure and assess treatment group differences.

Main Results:

• A composite outcome incorporating FVC% predicted, QLF-ZM, TDI, and HAQ-DI demonstrated a significant treatment effect favoring cyclophosphamide (p=0.005).
• Excluding FVC% predicted from the composite measure did not diminish the observed treatment effect (p=0.004).
• The composite outcome showed a stronger treatment effect compared to FVC alone.

Conclusions:

• A composite outcome measure integrating physiologic, structural, and patient-reported data is a more robust assessment tool for SSc-ILD treatment response.
• This approach may enhance the sensitivity of clinical trials in detecting treatment efficacy in SSc-ILD.