Background/Purpose

Systemic Sclerosis (SSc) is often associated with disability, which worsens over time. However, there is considerable heterogeneity in the rate of patients’ disability progression. The aim of the present study was to identify homogenous subpopulations of SSc patients with distinct trajectories of change in disability over a three-year period.

Methods

The sample included patients with limited and diffuse SSc (N = 1,125) participating in the Canadian Scleroderma Research Group Registry. As part of the Registry, patients are scheduled for annual follow-up visits. Patients with and without follow-up visits were included to account for potentially informative patient drop out. Growth mixture modeling (GMM) with robust maximum likelihood estimation was completed to identify groups of patients with distinct trajectories of disability over a three-year period, as measured by the Health Assessment Questionnaire-Disability Index (HAQ-DI; range: 0 (no disability) – 3 (severe disability)). Multinomial logistic regression was used to identify baseline sociodemographic and clinical variables that predicted membership in the latent growth trajectory classes. 

Results

Considering fit indices (AIC, sBIC, BLRT) and substantive interpretation (class proportions, entropy), the GMM analysis identified three distinct groups of patients based on their disability trajectories. Class 1 was comprised of 53.4% of the total sample, and Classes 2 and 3 were comprised of 35.3%, and 11.2% of the total sample, respectively. Based on trajectories of HAQ-DI scores the groups were named: Minimal Disability-Increasing (Class 1; baseline HAQ-DI: .27), Moderate Disability-Stable (Class 2; baseline HAQ-DI: 1.20), and Severe Disability-Stable (Class 3; baseline HAQ-DI: 2.04). In Class 1, HAQ-DI scores increased by .12 over three years. Patients in Class 3 had more finger ulcers, more breathing problems, and more gastrointestinal problems than patients in Class 2 or Class 1. In addition, patients in Class 3 were of older age, had shorter disease duration, and were more likely to be female and have diffuse disease than patients in Class 1.  Patients in Class 2, when compared to Class 1, had more finger ulcers, breathing problems, and severe Raynaud’s phenomenon, and were more likely to be older, female, and have diffuse disease.

Conclusion

Disability trajectories are not uniform across patients with SSc. Overall, patients with low baseline disability scores and disability progression had fewer finger ulcers, breathing problems, and gastrointestinal problems, less severe Raynaud’s phenomenon, were of younger age, male, had longer disease duration, and limited disease in comparison to the moderate and severe disability groups. The moderate and severe disability groups did not report significant disability progression, suggesting that for at least some patients with SSc, disability may reach a peak and then remain stable overtime.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/trajectories-of-disability-over-time-among-patients-with-systemic-sclerosis/