Prognostic factors and disease behaviour of pathologically proven fibrotic non-specific interstitial pneumonia

Non-specific interstitial pneumonia (NSIP) has heterogeneous characteristics in terms of background, disease behaviour and prognosis. This study of fibrotic NSIP (f-NSIP) aimed to elucidate prognosis and disease behaviour from the viewpoint of clinical background and determine whether long-term change of pulmonary function could provide useful prognostic information.

We analysed the medical records of 157 consecutive patients diagnosed with f-NSIP by surgical lung biopsy. Disease behaviour was categorized into two groups depending on long-term change of pulmonary function: progressive type (relative ≥5%/year decline in the slope of forced vital capacity and/or relative ≥7.5%/year decline in the slope of %diffusing capacity of lung carbon monoxide) or stable type. Predictors of disease behaviour and prognosis were determined using logistic and Cox regression models.

Our f-NSIP cohort included interstitial pneumonia with autoimmune features (IPAF) (36.9%), idiopathic (non-IPAF) (22.3%) and connective tissue disease-associated interstitial lung disease (40.8%). Multivariate analysis showed that idiopathic (non-IPAF) f-NSIP and progressive type disease were negative prognostic factors of mortality. Poor treatment response at 1 year was an independent predictor of progressive type disease, but was not related to survival. In terms of disease behaviour based on pulmonary function change, some patients with IPAF f-NSIP showed a progressive course.

Although an IPAF diagnosis was useful for identifying good prognosis in idiopathic f-NSIP, some idiopathic f-NSIP patients with or without IPAF showed progressive disease despite therapy. The definition of progressive type disease may be useful in clinical decision-making when determining therapy for f-NSIP.