Prognostic value of transbronchial lung cryobiopsy for the multidisciplinary diagnosis of idiopathic pulmonary fibrosis: a retrospective validation study

Background: Transbronchial lung cryobiopsy (TBLC) has been introduced recently in the diagnosis of interstitial lung diseases. We aimed to evaluate the prognostic significance of the distinction between idiopathic pulmonary fibrosis and other interstitial lung diseases with the use of TBLC data in multidisciplinary team (MDT) diagnosis.

Methods: In this single-centre, retrospective, investigator-initiated comparative study, we evaluated consecutive patients without a definite usual interstitial pneumonia pattern on high-resolution CT, who presented to the GB Morgagni Hospital (Forlì, Italy), and who underwent TBLC (Jan 1, 2011, to Dec 31, 2014) or surgical lung biopsy (SLB; Jan 1, 2002, to Dec 31, 2016). Three pathologists reviewed the specimens, masked to clinical information. MDT evaluation was done before and after biopsy. The primary endpoint was the prognostic significance of the MDT diagnostic separation between idiopathic pulmonary fibrosis and other interstitial lung diseases in patients undergoing TBLC. Mortality was evaluated by means of Cox regression analysis.

Findings: We evaluated 500 consecutive cases, 426 of which were included: 266 had TBLC and 160 had SLB. 189 patients had idiopathic pulmonary fibrosis, 143 had other fibrotic interstitial lung diseases, and 94 had non-fibrotic interstitial lung diseases. Patients undergoing TBLC had more comorbidities and better preserved lung function compared with those undergoing SLB; among patients with a final MDT diagnosis of idiopathic pulmonary fibrosis, patients undergoing TBLC were older, had more comorbidities, and had a different post-biopsy treatment profile than those who received SLB. The distinction between idiopathic pulmonary fibrosis and other interstitial lung diseases made by MDT diagnosis on the basis of TBLC biopsy had clear prognostic significance, with a 5-year transplant-free survival of 68% (95% CI 57-76) in patients with an MDT idiopathic pulmonary fibrosis diagnosis based on TBLC compared with 93% (87-96) in patients without an idiopathic pulmonary fibrosis diagnosis based on TBLC (hazard ratio 5·28, 95% CI 2·72-10·04; p<0·0001). This distinction remained statistically significant in a multivariate analysis controlling for age, sex, smoking status, comorbidities, pulmonary function, and high-resolution CT patterns (p=0·02).

Interpretation: TBLC makes an important diagnostic contribution in interstitial lung disease, on the basis of the prognostic distinction between idiopathic pulmonary fibrosis and other interstitial lung diseases when TBLC findings are included in multidisciplinary diagnosis.

Funding: None.