Derivation and validation of a simple multidimensional index incorporating exercise capacity parameters for survival prediction in idiopathic pulmonary fibrosis

INTRODUCTION

The gender-age-physiology (GAP) index is an easy-to-use baseline mortality prediction model in idiopathic pulmonary fibrosis (IPF). The GAP index does not incorporate exercise capacity parameters such as 6 min walk distance (6MWD) or exertional hypoxia. We evaluated if the addition of 6MWD and exertional hypoxia to the GAP index improves survival prediction in IPF.

METHODS

Patients with IPF were identified at a tertiary care referral centre. Discrimination and calibration of the original GAP index were assessed. The cohort was then randomly divided into a derivation and validation set and performance of the GAP index with the addition of 6MWD and exertional hypoxia was evaluated. A final model was selected based on improvement in discrimination. Application of this model was then evaluated in a geographically distinct external cohort.

RESULTS

There were 562 patients with IPF identified in the internal cohort. Discrimination of the original GAP index was measured by a C-statistic of 0.676 (95% CI 0.635 to 0.717) and overestimated observed risk. 6MWD and exertional hypoxia were strongly predictive of mortality. The addition of these variables to the GAP index significantly improved model discrimination. A revised index incorporating exercise capacity parameters was constructed and performed well in the internal validation set (C-statistic: 0.752; 95% CI 0.701 to 0.802, difference in C-statistic compared with the refit GAP index: 0.050; 95% CI 0.004 to 0.097) and external validation set (N=108 (C-statistic: 0.780; 95% CI 0.682 to 0.877)).

CONCLUSION

A simple point-based baseline-risk prediction model incorporating exercise capacity predictors into the original GAP index may improve prognostication in patients with IPF.

[Face to a bilateral pneumothorax, just scratch your head!]

Head and neck skin angiosarcoma is a rare and aggressive tumor (1 % of head and neck tumors). Prognosis remains poor, with a 5-year survival rate ranging from 10 to 54%, depending on the initial stage. Metastatic disease markedly worsens the prognosis. Metastatic lung involvement is classic and can take on several forms. The cystic form is responsible for numerous complications, particularly pneumothorax. In this case, an 83-year-old patient was diagnosed with bilateral pneumothorax complicating cystic interstitial lung disease, which was revealed by hemoptoic sputum. Skin examination revealed two large necrotic lesions of the calvaria. Anatomo-pathological examination confirmed cutaneous angiosarcoma on both skin biopsy and lung resection. At a metastatic stage, only systemic treatment with paclitaxel can be proposed. The clinical course was unfavorable, leading to death before any specific treatment. This observation highlights the importance of a complete clinical skin examination in the assessment of pulmonary cystic lesions.