Background Interstitial lung disease (ILD) is one of the leading causes of death in systemic sclerosis (SSc) patients. The incidence and predictors of ILD determined by High-Resolution Computed Tomography (HRCT) in patients with early SSc have been inconclusive.
Objectives The aims of this study were to (1) examine the prevalence of ILD determined by HRCT; (2) compare the differences of the calculated HRCT scores between DcSSc and LcSSc; (3) compare the differences of incidence rate (IR) of ILD among the two subtypes and (4) determine the factors associated with ILD complication of early SSc.
Methods We used an inception cohort of SSc patients seen at the Rheumatology clinic, Chiang Mai University, between January 2010 and June 2014. All patients were assessed for demographic data, clinical manifestations, laboratory testing, and underwent HRCT at study entry and every 12 months thereafter. ILD was determined by HRCT. The extent of ground glass (GG), lung fibrosis (Fib), bronchiectasis (B) and honeycombing (HC) was scored and then were aggregated to produce a total CT perfusion score (CT-total)1.
Results One hundred and thirteen patients (66 females) with a mean (SD) age of 53.4 years (8.4) and mean (SD) disease duration (from non-Raynaud's phenomenon: NRP) 12.9 months (10.3) at cohort entry were enrolled during a mean (SD) observation period of 2.2 years (1.4). Of 113 patients, there were 89 (78.8%) patients with DcSSc, 69 (61.1%) without chest symptom, 91 (80.5%) with positive anti Scl-70 and 7 (6.2%) with positive anti-centromere antibodies. Mean (SD) values were: modified Rodnan's skin score 19.4 (11.4); %SpO2 96.8 (2.6); hemoglobin 12.4 (1.8) g/dl; creatinine 0.9 (0.3) mg/dl; CK 351.4 (509.4) U/L; and ESR 41.2 (30.1) mm/hr. At enrollment, there were significant differences between DcSSc and LcSSc in the prevalence of nonspecific interstitial pneumonitis (NSIP) [61.8%vs 45.8%], usual interstitial pneumonitis (UIP) [16.9% vs 0%], normal parenchyma [18.0% vs 45.8%], and nonspecific findings [3.4% vs 8.3%];(p=0.004). Of 80 patients diagnosed ILD, 53 (66.2%) was found within the first year from NRP. Patients with DcSSc had significantly higher calculated total GG (3.9±4.2 vs 1.8±2.5), t-Fib (4.1±3.3 vs 2.1±2.4), t-B (2.2±3.2 vs 0.4±1.2), and CT-total scores (10.3±9.4 vs 4.4±5.6) than those of LcSSc (p<0.01); although DcSSc had shorter duration from NRP to underwent HRCT than LcSSc (11.4±9.4 vs 18.7±11.6 months, p=0.001). There were significant differences of the IR of ILD since NRP between DcSSc and LcSSc (58.8 vs 17.3 per 100 person-years, p<0.001). Cox-regression analysis revealed that DcSSc subtype [HR 2.12 (95% CI1.1, 4.47)], CK>300 [HR 1.75 (95%CI 1.1, 2.94)] were predictors of ILD, whereas positive anti-centromere [HR 0.12 (95%CI 0.02, 0.95)] and age [HR 0.96 (95%CI 0.93, 0.99)] showed negatively associated.
Conclusions Early SSc patients with DcSSc subtype had higher incidence rate of ILD as well as had more severe HRCT scores than those of LcSSc. DcSSc subtype, high CK and absent anti-centromere antibody predicted future pulmonary fibrosis of early SSc patients.
Patiwetwitoon S, et al. J Clinical Rheumatol 2012.
Disclosure of Interest None declared