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Endobronchial Optical Coherence Tomography Aids Diagnosis of Interstitial Lung Disease

Key findings

  • This comparative, blinded, prospective, single-center study evaluated the diagnostic accuracy of endobronchial optical coherence tomography (EB-OCT) for microscopic diagnosis of interstitial lung disease (ILD) in 27 patients
  • EB-OCT accurately distinguished usual interstitial pneumonia (UIP) from non-UIP ILD with sensitivity and specificity of 100% compared with histopathologic diagnosis of UIP on concurrent surgical lung biopsy and clinical diagnosis of idiopathic pulmonary fibrosis on clinical follow-up
  • EB-OCT diagnosis of specific fibrotic ILD patterns showed high agreement with the results of concurrent surgical lung biopsy (weighted κ, 0.87)
  • EB-OCT procedural and interpretation skills were acquired with minimal training by physicians who were previously unfamiliar with the modality
  • This study provides evidence of the utility of EB-OCT as a safe, low-risk method for microscopic diagnosis of ILD, particularly histopathologic UIP and clinical idiopathic pulmonary fibrosis

Early, accurate diagnosis of interstitial lung disease (ILD) is critical for prognostication and choice of therapy. Standard diagnostic methods face challenges, though: high-resolution computed tomography (HRCT) has limited resolution and surgical lung biopsy (SLB) carries risks of morbidity and mortality. Transbronchial lung cryobiopsy (TBLC) is a less invasive alternative to SLB, but its use has been limited by concerns about pneumothorax and bleeding, sampling error and other concerns.

Endobronchial optical coherence tomography (EB-OCT) is a real-time imaging technique, conducted through the working channel of a standard diagnostic bronchoscope, and evaluates the peripheral lung without the need for tissue removal. In the American Journal of Respiratory and Critical Care MedicineLida P. Hariri, MD, PhD, pulmonary pathologist in the Department of Pathology and Division of Pulmonary and Critical Care Medicine at Massachusetts General Hospital, Sreyankar Nandy, PhD, research associate in the Division of Pulmonary and Critical Care Medicine at Mass General, and Rebecca A. Raphaely, MD, former clinical pulmonary fellow in the division, and colleagues report promising results from a study of EB-OCT for diagnosis of ILD.

Study Methods

The 27 participants in the blinded, prospective, single-center study were enrolled between November 2015 and March 2020. They were ages 21 or older, had a low-confidence diagnosis of fibrotic ILD based on HRCT, and required SLB in the opinion of the treating pulmonologist.

Patients underwent EB-OCT during clinical bronchoscopy prior to SLB or TBLC. The nine bronchoscopists received 10 minutes of standardized training on EB-OCT. A pathologist with expertise in ILD and EB-OCT interpretation was present during the procedure to confirm subpleural positioning of the EB-OCT catheter and ensure adequate sampling and image quality.

The EB-OCT results were interpreted by four pathologists: the expert EB-OCT reader and three novice readers who had expertise in ILD but no prior experience with OCT imaging; the novice readers participated in a three-hour training with the expert reader. All readers were blinded to each subject's SLB histopathology diagnosis and all other EB-OCT interpretations.

Two independent pathologists with expertise in ILD provided a histopathology diagnosis on SLB for each subject. In cases of discrepancy amongst the two pathologists on SLB (30% of cases), a third pathologist provided a diagnosis to reach a majority diagnosis on SLB.

The treating pulmonologist determined a clinical follow-up diagnosis for each patient as part of clinical care after SLB. An independent pulmonologist confirmed the diagnosis.

All pathologists and pulmonologists were blinded to EB-OCT results.

12 patients were diagnosed with usual interstitial pneumonia (UIP, 44.5%) and all 12 had a clinical follow-up diagnosis of idiopathic pulmonary fibrosis (IPF). 15 were diagnosed non-UIP/IPF ILD (55.5%).

Procedural Results

  • No adverse events were associated with EB-OCT
  • The average bronchoscopy time for EB-OCT was 9.5 minutes, substantially less than for standard SLB
  • EB-OCT was conducted in diseased regions in all lung lobes without difficulty, including assessment of multiple locations within the same lobe and across multiple lobes in both lungs, neither of which can be done easily with SLB or TBLC

EB-OCT Performance

Compared with the histopathologic diagnosis of UIP and clinical follow-up diagnosis of IPF, EB-OCT diagnosis of UIP achieved:

  • According to the expert reader: Sensitivity, 100%; specificity, 100%; positive predictive value, 100%; negative predictive value, 100%
  • Novice reader 1—100%; 100%; 100%; 100%
  • Novice reader 2—100%; 100%; 100%; 100%
  • Novice reader 3—67%; 100%; 100%; 78%

EB-OCT diagnosis of specific fibrotic ILD patterns showed high agreement with SLB results (weighted κ, 0.87).

The Future of ILD Diagnostic Workup

This study supports the use of EB-OCT as a complement to HRCT and an alternative to SLB for diagnosing ILDs, notably histopathologic UIP and clinical IPF. It also indicates physicians can easily be trained to acquire and interpret EB-OCT data, suggesting the imaging method could be expanded readily to other sites. Planning for larger, multicenter trials is underway.

100%
sensitivity of endobronchial optical coherence tomography for diagnosing usual interstitial pneumonia when read by an expert pathologist

100%
specificity of endobronchial optical coherence tomography for diagnosing usual interstitial pneumonia when read by an expert pathologist

100%
positive predictive value of endobronchial optical coherence tomography for diagnosing usual interstitial pneumonia when read by an expert pathologist

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