Factors affecting treatment outcome in patients with idiopathic nonspecific interstitial pneumonia: a nationwide cohort study

Abstract

Background: The effects of corticosteroid-based therapy in patients with idiopathic nonspecific interstitial pneumonia (iNSIP), and factors affecting treatment outcome, are not fully understood. We aimed to investigate the long-term treatment response and factors affecting the treatment outcome in iNSIP patients from a multi-center study in Korea.

Methods: The Korean interstitial lung disease (ILD) Study Group surveyed ILD patients from 2003 to 2007. Patients were divided into two groups to compare the treatment response: response group (forced vital capacity (FVC) improves ≥10% after 1 year) and non-response group (FVC <10%). Factors affecting treatment response were evaluated by multivariate logistic regression analysis.

Results: A total of 261 patients with iNSIP were enrolled, and 95 patients were followed-up for more than 1 year. Corticosteroid treatment was performed in 86 patients. The treatment group showed a significant improvement in lung function after 1-year: FVC, 10.0%; forced expiratory volume (FEV₁), 9.8%; diffusing capacity of the lung for carbon monoxide (DLco), 8.4% (p < 0.001). Sero-negative anti-nuclear antibody (ANA) was significantly related with lung function improvement. Sero-positivity ANA was significantly lower in the response group (p = 0.013), compared to that in the non-response group. A shorter duration of respiratory symptoms at diagnosis was significantly associated with a good response to treatment (p = 0.018).

Conclusion: Treatment with corticosteroids and/or immunosuppressants improved lung function in iNSIP patients, which was more pronounced in sero-negative ANA and shorter symptom duration patients. These findings suggest that early treatment should be considered in iNSIP patients, even in an early disease stage.

Keywords: Non-specific interstitial pneumonia; Pulmonary lung function; Treatment.

Fig. 1

Flow chart of the study population. Initially, 2186 patients with interstitial lung disease (ILD) were enrolled by the Korean study group between January 1, 2003, and December 31, 2007. A total of 261 surgically diagnosed patients with non-specific interstitial pneumonia (NSIP) were analyzed in this study; 1925 patients with a different diagnosis other than NSIP were excluded from this study. One hundred and fifty seven patients were followed-up within 1 year, and 95 patients were followed-up after >1 year. Of these 95 patients, nine were in the conservative care group, and 86 in the treatment group. The treatment group was defined as those prescribed corticosteroid and/or immunosuppressant therapy, and conservative care group was defined as those who were only prescribed medication for symptom control. IPF: idiopathic pulmonary fibrosis, COP: cryptogenic organizing pneumonia, AIP: acute interstitial pneumonia, DIP: desquamative interstitial pneumonia, RB-ILD: respiratory bronchiolitis-associated interstitial lung disease, LIP: lymphocytic interstitial pneumonia

Fig. 2

Changes in lung function over time between the response group and non-response group. a Change in functional vital capacity (FVC) (%) over time between the two groups (p < 0.001, Mean ± standard error (SE), b Change in the diffusing capacity of the lung for carbon monoxide (DL_CO) (%) over time between the two groups (p = 0.002, Mean ± SE)