Bronchiolocentric interstitial pneumonia is a more accurate ILD classification than hypersensitivity pneumonitis: CON

We believe that bronchiolocentric interstitial pneumonia (BIP), as proposed in the 2025 update of a classification for interstitial pneumonias (IPs), is a less accurate interstitial lung disease (ILD) classification than hypersensitivity pneumonitis (HP) when ­reporting patterns identified on high-resolution computed tomography (HRCT) scans and/or lung biopsies.1 Similarly, idiopathic BIP (MDD-iBIP) is a less accurate ILD diagnosis than HP following multidisciplinary discussion (MDD-HP) in patients who satisfy morphologic criteria for a definite or high-probability HP diagnosis in whom no causative exposure has been identified.2,3 Ongoing scientific dialogue and well-designed, unbiased studies focused on meaningful and measurable outcomes are essential to resolving our differences. High-resolution computed tomography and histopathologic patterns are fundamental to multidisciplinary diagnosis of HP, as outlined in the 2020 American Thoracic Society (ATS)/Japanese Respiratory Society (JRS)/Associación Latinoamericana de Tórax (ALAT) and 2021 CHEST guidelines.2,3 Diagnostic algorithms in both help clinicians worldwide reproducibly diagnose MDD-HP, including in a subset of patients for whom no exposure is discovered (Figure 1).4,5 Several studies demonstrate that radiologically and pathologically defined HP patterns predict MDD-HP in a manner relatively agnostic to exposure history.4,6,7 Retrospective review of 179 patients discussed at a single institution in a formal MDD process that included comprehensive exposure assessment and chest computed tomography (CT) imaging showed higher specificity (98% and 100%) and positive predictive values (PPVs) (73% and 100%) for radiologic and histologic HP patterns, respectively, compared to an exposure history (PPV 55.8%) when measured against MDD-HP diagnoses.6 Usual interstitial pneumonia (UIP) and nonspecific interstitial pneumonia (NSIP) were different, showing lower specificity (77.8% and 72.5%) and PPVs (33.3% and 8.3%) in predicting MDD diagnoses of idiopathic pulmonary fibrosis (IPF) and idiopathic NSIP, respectively. A multicenter study used 2020 HP guidelines to show that an exposure history, typical or compatible HRCT pattern, and probable or typical histology were the most significant predictors of MDD-HP in multivariate regression analysis.4 A majority of 45 international expert pulmonologists ranked air trapping on HRCT and poorly formed nonnecrotizing granulomas on lung biopsy as the most important diagnostic elements in patients who lacked an exposure history; most agreed that a histopathologic HP pattern alleviated the need for additional testing.8 These and similar observations align with ATS/JRS/ALAT and CHEST guidelines proposing that a definite or high-probability MDD-HP diagnosis is appropriate in patients who lack an exposure history with typical or compatible HRCT and a typical lung biopsy HP pattern (Figure 1).2,3