Organizing pneumonia and lymphoplasmacytic inflammation predict treatment response in idiopathic pulmonary fibrosis

Aims: To identify individual histopathological features within usual interstitial pneumonia pattern that predict responsiveness to immunosuppressive therapy. Methods and results: Fifty-six retrospectively confirmed usual interstitial pneumonia pattern surgical lung biopsy specimens from subjects with idiopathic pulmonary fibrosis treated with corticosteroid and cytotoxic therapy were included. Eleven prospectively defined histopathological features were evaluated by two expert pulmonary pathologists. Regression analysis identified predictors of response to therapy, as defined by the change in percent predicted forced vital capacity over 6 months. Additional end-points were change in dyspnoea score over 6 months, and survival time. Improvement in percent predicted forced vital capacity was associated with lymphoplasmacytic inflammation, while worsening of percent predicted forced vital capacity was associated with the presence of organizing pneumonia and fibroblast foci. Worsening dyspnoea was associated with fibroblast foci. Survival time was associated with age and baseline percent predicted forced vital capacity, but not with any individual histopathological feature. Conclusions: In pathological usual interstitial pneumonia pattern, the presence of lymphoplasmacytic inflammation predicts responsiveness to immunomodulatory therapy, while airspace organization predicts lack of response.