Amount of elastic fibers predicts prognosis of idiopathic pulmonary fibrosis.

BACKGROUND

Elastic fibers enhance the stiffness of fibrotic tissues, but their role in the pathophysiology of idiopathic pulmonary fibrosis (IPF) has not been fully examined. The aim of this study was to determine clinical significance of the amount of elastic fibers in IPF.

METHODS

We studied the surgical lung biopsy specimens of 43 patients with IPF. Histological specimens were stained using the Elastica Van Gieson method and digital images were taken. The number of pixels containing elastic fibers was divided by the number occupied by fibrotic tissue, from which the proportion of elastic fibers (elastic fiber score, %) was calculated. The relationships between the elastic fiber score and clinical, radiological and pathological findings, and prognosis were explored.

RESULTS

The median elastic fiber score was 10.9% (range 5.1-23.3%). Scores were inversely correlated with % predicted forced vital capacity (r -0.451, p-value 0.003) and positively correlated with decline in forced vital capacity over 12 months (r -0.475, p-value 0.033). Furthermore, elastic fiber score correlated with the extent of fibrotic lesions assessed on high resolution computed tomography as well as the degree of collagen deposition on biopsy specimens. Patients with high elastic fiber scores had significantly worse outcomes than those with low scores (5-year survival rate was 48.7% and 84.0%, respectively, p-value 0.024), and elastic fiber score was an independent predictor of poor prognosis (hazard ratio 1.21, p-value 0.005).

CONCLUSION

The amount of elastic fiber in fibrotic tissue is a prognostic indicator in patients with IPF.