Early, accurate diagnosis of interstitial lung disease (ILD) informs prognosis and therapy, especially in idiopathic pulmonary fibrosis (IPF). Current diagnostic methods are imperfect. HRCT resolution is limited while surgical lung biopsy (SLB) carries risks of morbidity/mortality. Endobronchial optical coherence tomography (EB-OCT) is a low-risk, bronchoscope-compatible modality that images large lung volumes in vivo with microscopic resolution, including subpleural lung, and has the potential to improve the diagnostic accuracy of bronchoscopy for ILD diagnosis.
We performed a prospective diagnostic accuracy study of EB-OCT in ILD patients with a low-confidence diagnosis undergoing SLB. Primary endpoints were EB-OCT sensitivity/specificity for diagnosis of the histopathologic pattern of usual interstitial pneumonia (UIP) and clinical IPF. The secondary endpoint was agreement between EB-OCT and SLB for diagnosis of the ILD fibrosis pattern.
EB-OCT was performed immediately prior to SLB. The resulting EB-OCT images and histopathology were interpreted independently by blinded, independent pathologists. Clinical diagnosis was obtained from the treating pulmonologists after SLB, blinded to EB-OCT.
We enrolled 31 patients, and four were excluded due to inconclusive histopathology or lack of EB-OCT data. Twenty-seven patients were included in the analysis (16 men, average age: 65.0 years): twelve were diagnosed with UIP and fifteen with non-UIP ILD. Average forced vital capacity and DLCO were 75.3% (SD:18.5) and 53.5% (SD:16.4), respectively. Sensitivity and specificity of EB-OCT was 100% (95% CI: 75.8-100.0%) and 100% (79.6-100%), respectively, for both histopathologic UIP and clinical diagnosis of IPF. There was high agreement between EB-OCT and histopathology for diagnosis of ILD fibrosis pattern (weighted κ: 0.87, (0.72-1.0)).
EB-OCT is a safe, accurate method for microscopic ILD diagnosis, as a complement to HRCT and alternative to SLB.