Background: Various visual semi-quantitative staging systems based on high-resolution computed tomography are used to evaluate inflammatory rheumatologic disease-associated interstitial lung disease. We aimed in this retrospective study to evaluate whether tomographic fibrosis score, a new visual semi-quantitative staging system, was a predictor of mortality and the relationship between tomographic fibrosis score and respiratory function tests in patients with systemic sclerosis-associ- ated interstitial lung disease.
Methods: The patients who have been followed up at a single-center rheumatology clinic for the last 5 years and met the American College of Rheumatology / European League Against Rheumatism (ACR-EULAR) 2013 systemic sclerosis classification criteria were included in the study. Clinical data were obtained retrospectively from patient records, including patients' characteristics, pulmonary function test (forced vital capacity), diffusing capacity of the lung for carbon monoxide test, high-reso- lution computed tomography results, medication history, and serological test results. High-resolution computed tomography of the patients diagnosed with interstitial lung disease were assessed for the study. The radiologists scored the extent of parenchymal abnormalities (ground glass opacification, reticulation, honeycombing, and consolidation) and calculated tomographic fibrosis score and also traction bronchiectasis score for each patient.
Results: Fifty-two patients (46 female, median age 60 (Q1-Q3:47-66) years) were included in this study. The median disease duration, follow-up time, interstitial lung disease duration, and time from sys- temic sclerosis diagnosis to interstitial lung disease diagnosis were 80 (59-143) months, 78 (50-119) months, 63 (43-81) months, and 4 (0-58) months, respectively. The median tomographic fibrosis score and traction bronchiectasis score of the patients were 3.08% (1.33-8.06) and 0 (0-2), respectively. There was a moderate direct correlation between tomographic fibrosis score and traction bronchiectasis score (r = +0.472, P < .001). Additionally, there was a mod- erate inverse correlation between tomographic fibrosis score and diffusing capacity of the lung for carbon monoxide at diagnosis (r = -0.554, P = .011). During the follow-up period, 12 (23%) patients died. Kaplan-Meier Test (P = 0.009) and Cox regression analysis (B: 4.673, 95% confidence interval, 1.321-16.529, P = .017) revealed that tomographic fibrosis score ≥ 5% was associated with mortality. Multivariate analysis was not performed due to the small number of patients.
Conclusion: An inverse relationship was found between tomographic fibrosis score and diffusing capacity of the lung for carbon monoxide at diagnosis. The odds ratio for mortality was 4.7 when tomographic fibrosis score was ≥5%. Tomographic fibrosis score may be useful for predicting mor- tality and respiratory function in patients with systemic sclerosis-associated interstitial lung disease.