Background Interstitial lung disease (ILD) is one of the major types of lung involvement in systemic sclerosis (SSc). Affected patients have a worse prognosis than patients with SSc who are free of pulmonary involvement. Therefore, it is important to explore determinants of this organ complication.
Objectives To found possible determinants of ILD in SSc patients.
Methods A cross-sectional study was conducted in 104 SSc patients (2013 ACR/EULAR criteria) from a university hospital of Portugal. The analyzed variables were: age, sex, age at disease onset, disease duration, antinuclear antibodies (ANA), topoisomerase I DNA (Scl70) and anticentromere antibodies (ACAs) status, Raynaud phenomenon, areas of skin sclerosis (limited was divided into sclerodactyly or proximal to the metacarpophalangeal (MCP) joints), digital ulcers (DU), digital pitting scar and telangiectasia status, diffusion capacity of carbon monoxide transfer/alveolar volume (DLCO/VA, % of the predicted value) at diagnosis and esophagus involvement. Descriptive statistics were calculated for several demographic and clinical characteristics. Pearson or Spearman correlation and chi-square or Fisher's exact test was used for the assessment of the correlation between ILD and the different continuous and categorical variables. Subsequently, binary logistic regression analysis (method enter) was carried out using the ILD as the dependent variable. As independent variables, were included variables that had clinical or statistical significance.
Results Most (89.4%) of patients were women; mean (SD) age was 59 (±13) years. Mean age at diagnosis was 51 (±13) years with disease duration median (min;max) of 6 (0;38) years. Ninety-three (89.4%) patients had limited (lcSSc) scleroderma. Most (98.1%) patients had ANA positive (mainly centromere (n=61) followed by nucleolar pattern (n=15)), 61 (58.7%) patients were ACAs positive and 21 (20.2%) positive for Scl70 antibodies. DLCO/VA mean at SSc diagnosis was 74.8% (±13.6). Twenty-three (22.1%) patients had ILD (most NSIP pattern) and 64 (61.5%) had esophagus involvement. Correlation coefficients with statistical significance were noted for disease duration and age however, these were weak (rô=0.22, p=0.03 and r=0.29, p=0.004; respectively). For categorical variables we observed statistical significance for SSc subgroups (ILD prevalence of 15.1% in lcSSc vs 72.7% in diffuse SSc; p<0.001), ACAs and Scl70 serology (6.6% in ACAs vs 57.1% in Scl70 positive patients; p<0.001) and DU (33.3% if history vs 15.5% if without history of DU, p=0.02). Correlation of ILD with DLCO/VA at SSc diagnosis and sex had not statistical significance (p=0.064). In logistic regression the following variables were introduced: age, disease duration, SSc subgroups, ACAs and Scl70 serology, skin sclerosis proximal to the MCP joints, DU status and DLCO/VA at SSc diagnosis. The analysis showed that the age (OR=1.13,p=0.003), SSc subgroups (OR=22.95,p<0.001) and ACAs status (OR=0.08,p=0.001) influence the ILD in the model.
Conclusions Our results suggest that higher age and diffuse sclerosis increased ILD risk and ACAs decreases. A prospective longitudinal study with a larger sample is desirable to confirm these results.
Disclosure of Interest None declared
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