FRI0433 Assessing mortality models in systemic sclerosis related interstitial lung disease
Authors: R.L. Mango, E.L. Matteson, C.S. Crowson, J.H. Ryu, A. Makol
Journal: Annals of the Rheumatic Diseases (2018)

<h3>Background</h3> Interstitial lung disease (ILD) is a major cause of morbidity and mortality in systemic sclerosis (SSc). However, the severity of lung involvement can vary widely, and current evidence-based treatment options have modest benefit. Prognosis assessment is particularly important for initial management decisions at the time SSc-ILD is diagnosed. There are now multiple mortality models available for use in SSc-ILD which utilise patient's baseline parameters <h3>Objectives</h3> The Gender, Age, and Lung Physiology (GAP) model,<sup>1</sup> interstitial lung diseases –GAP (ILD-GAP) model,<sup>2</sup> and the Smoking history, Age, and Diffusion capacity of the Lung (SADL) model<sup>3</sup> were compared using a systemic sclerosis-ILD (SSc-ILD) cohort to evaluate which best determined prognosis. <h3>Methods</h3> The models were applied to a cohort of patients with SSc (meeting the 2013 ACR/EULAR classification criteria) seen at a tertiary care centre within 1 year of ILD diagnosis from 2000–2013. Demographics, clinical characteristics, and mortality were recorded. The performance of the models was assessed using standardised mortality ratios (SMR) of observed vs. predicted outcomes for calibration, and concordance (c)-statistics for discrimination. <h3>Results</h3> The cohort included 179 patients with SSc-ILD. Mean age at ILD diagnosis was 57.8 years. There was a female predominance (73%). The mean length of follow up after ILD diagnosis was 4.3 years (SD 4.0). Based on high resolution chest CT (or biopsy when available), 147 (83%) were characterised as nonspecific interstitial pneumonia (NSIP), 31 (17%) as usual interstitial pneumonia (UIP), 1 as unclassifiable ILD. A history of smoking was noted in 49%, and this was not associated with ILD pattern (former/current 46% in NSIP vs. 61% in UIP, p=0.11). Pulmonary hypertension (PHTN) was noted in 66 (49%) at baseline, and this did not differ between ILD subtypes. 84% had limited cutaneous SSc, 9% had diffuse cutaneous, and 7% SSc sine scleroderma. SSc specific serologies (i.e., SCL-70, centromere, and/or RNA Pol III) were positive in 73 (43%) patients, somewhat more common in NSIP than UIP (47% vs 26%; p=0.034). During a median of 3.2 years of follow-up, 65 patients died. SSc-ILD patients with UIP had a higher mortality than those with NSIP (hazard ratio: 2.27; 95% CI: 1.03–4.97). Other risk factors for progression included baseline DLCO (p&lt;0.001), FVC (p&lt;0.001) and PHTN (p=0.012). All 3 models had comparable discrimination (c=0.72, 0.72, and 0.70, respectively). Figure 1 shows the differential mortality based on the GAP and SADL staging systems. (Note the staging in the GAP and ILD-GAP models are identical.) Regarding calibration, the ILD-GAP model underestimated mortality (SMR: 1.5; 95% CI: 1.05–2.14). Calibration was acceptable for SADL (SMR: 0.77; 95% CI: 0.54–1.10) and GAP (SMR: 0.90; 95% CI: 0.63–1.29). The SADL model overestimated mortality in Stage III ILD. <h3>Conclusions</h3> The ILD-GAP model underestimated mortality, and the SADL model overestimated mortality in certain subgroups. However, the GAP model performed well in this cohort, providing the best prognostic information for SSc-ILD. <h3>References</h3> [1] Ley B, et al. Annals of internal medicine2012;156(10):684–691. [2] Ryerson CJ, et al. Chest2014;145(4):723–728. [3] Morisset J, et al. Chest2017;152(5):999–1007. <h3>Disclosure of Interest</h3> None declared