Interstitial Lung Disease Section
Diagnosis of idiopathic pulmonary fibrosis: Is tissue still an issue?
Per ATS/ERS/JRS/ALAT guidelines, diagnosis of IPF requires exclusion of known causes of interstitial lung disease (ILD) and either the presence of a usual interstitial pneumonia (UIP) or probable UIP pattern on HRCT scan or specific combinations of HRCT scan and histopathologic patterns. Surgical lung biopsy (SLB) is the gold standard for histopathologic diagnosis.
The recent update (Raghu, et al. Am J Respir Crit Care Med. 2022;205[9]:1084-92) made a conditional recommendation for transbronchial lung cryobiopsy (TBLC) as an acceptable alternative to SLB in patients with undetermined ILD. Systematic analysis revealed a diagnostic yield of 79% (85% when ≥ 3 sites were sampled) by TBLC compared with 90% on SLB. With consideration of this diagnostic yield vs the risk of pneumothorax, severe bleeding, and procedural mortality, TBLC is an attractive tool compared with SLB. Overall, the utility of TBLC remains limited to experienced centers due to dependence on proceduralist and pathologist skills for optimal success and more data are awaited.
Dr. Kevin Dsouza
No recommendation was made for or against the use of genomic classifiers (GC) for the diagnosis of UIP in patients with undetermined ILD undergoing transbronchial biopsy. Although, meta-analysis revealed a specificity of 92%, this may be driven by patient enrichment with a high probability for UIP population. GC has the potential to reduce SLB-associated risks and provide diagnostic information for multidisciplinary discussion in certain scenarios. However, limitations arise from the inability to distinguish specific ILD subtype associated with the UIP pattern; further improvement in sensitivity and understanding of downstream consequences of false-negative results is necessary.
Kevin Dsouza, MD
Fellow-in-Training