Idiopathic Pulmonary Fibrosis Update: Reconciliation with Hypersensitivity Pneumonitis Guidelines Required?

To the Editor:

Clinicians welcome the updated idiopathic pulmonary fibrosis (IPF) clinical practice guidelines recently published in the Journal (1). Raghu and a multidisciplinary group of experts did a great job at providing evidence-based recommendations and suggestions to guide clinicians in the diagnosis and management of IPF and progressive pulmonary fibrosis. However, the updated IPF guidelines do not emphasize the role of ruling out known causes of usual interstitial pneumonia (UIP) or probable UIP patterns on high-resolution computed tomography (HRCT) of the chest, as previous guidelines did (2). In particular, they do not address the role of BAL in the diagnosis of hypersensitivity pneumonitis (HP), arguably the most important differential diagnosis of IPF. Furthermore, in the diagnostic algorithm proposed in the guidelines in Figure 10, the authors do not recommend or suggest any additional testing in patients with UIP or probable UIP pattern on HRCT to rule out HP (1).

Hence, how do current guidelines reconcile with recent HP guidelines (3, 4), which suggest that, in patients with UIP or probable UIP pattern on HRCT (called indeterminate for HP pattern in the HP guidelines), BAL is required to define the diagnosis? It would have been very helpful if the current guidelines had provided further clarification on this matter.