Background/Purpose: Systemic sclerosis (SSc) is an autoimmune disease characterized by skin thickening, vascular lesions and fibrotic changes in various organs, mainly the lungs, heart, intestinal tract, kidneys, muscles and joints. Pulmonary complications of SSc are one of the leading causes of morbidity and mortality. Interstitial lung disease (ILD) is among the most common forms of lung disease associated with SSc. To date, no published study has generated population-based estimates of the prevalence of SSc-ILD in Canada. The objective of this study was to develop prevalence and survival estimates of SSc and SSc-ILD in Ontario, Canada using administrative data over 10 years.

Methods: Adult patients diagnosed with SSc between April 1, 2008 and March 31, 2018 were identified from the National Ambulatory Care Reporting System (NACRS) and Discharge Abstract Database (DAD) administrative databases, using ICD 10 CA codes. Patients with SSc were identified first, using M34 ICD-10 CA codes (M34.0, M34.1, M34.2, M34.8, and M34.9). SSc-ILD patients were identified if an additional one of J84.1, J84.8, J84.9 or J99.1 codes for lung disease was used after the SSc diagnosis. Prevalence estimates were determined for both SSc and SSc-ILD, based on the population of all eligible Ontario adults (~11.0 million as of fiscal 2017). Descriptive statistics and Kaplan Meier survival curves were generated.

Results: There were 3,111 unique patients identified as having SSc over 10 years. Of those, 559 (18%) were further identified as having SSc-ILD. At the start of fiscal year 2017/18 (final year of the cohort), there were 2,114 prevalent SSc cases for a cumulative prevalence of 19.12 per 100,000 persons from 2008/9 to 2017/18.  Over the same time frame, there were 257 prevalent cases of SSc-ILD, generating a prevalence of 2.32 cases per 100,000 persons. At index date, mean age was approximately 57 and 58 years of age for SSc and SSc-ILD patients with 84% and 80% females in the groups. The survival rates at one, five and ten years after diagnosis for the SSc group were 84.96%, 64.45% and 44.88%, respectively. The SSc-ILD group survival rates at one, five and ten years were lower, at 77.12%, 44.41% and 22.02%, respectively.

Conclusion: This study provides the first population based estimates of SSc-ILD in Canada. Results confirm that the prevalence of SSc-ILD may fall within a Canadian threshold for drugs for ‘other’ rare disease. It also demonstrates the poor survival in SSc and especially when SSc-ILD is present.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/prevalence-and-survival-of-systemic-sclerosis-ssc-and-associated-interstitial-lung-disease-ild-in-ontario-canada-over-10-years/