USA: The American College of Chest Physicians (CHEST) has released a new guideline on the diagnosis and evaluation of hypersensitivity pneumonitis (HP).
The purpose of this analysis is to provide evidence-based and consensus-derived guidance for clinicians to improve individual diagnostic decision-making for hypersensitivity pneumonitis (HP) and decrease diagnostic practice variability.
The systematic review of the literature based on 14 PICO questions resulted in 14 key action statements: 12 evidence-based, graded recommendations and 2 ungraded consensus-based statements. All evidence was of very low quality.
Occurring at any age, HP is an immunologically mediated form of lung disease resulting from inhalational exposure to a large variety of environmental and/or occupational inciting antigens (typically fungal, bacterial, avian). Over the years, the categorization of HP based on clinical features and disease duration coupled with traditional diagnostic criteria has been unhelpful, even when accurate, when separated from a probabilistic diagnostic reasoning approach and multidisciplinary consensus.
"Guidelines for medical diagnoses are fundamental to better align diagnostic approaches across practicing institutions," says Evans Fernández, MD, MS, a pulmonologist at National Jewish Health. "Along with streamlining the approach to diagnosing HP, the guidelines also provide a diagnostic algorithm incorporating the evidence and informed by expert consensus, to aid physicians in gauging the probability of HP."
"By outlining a patient-centered and interdisciplinary diagnostic approach to a confident or working HP diagnosis, these guidelines will serve as a central source to help optimize diagnostic consistency and decision-making in HP across multidisciplinary teams and among clinicians," wrote the authors.
Key recommendations include:
In patients with suspected hypersensitivity pneumonitis (HP), gathering a thorough clinical history of exposures focused on establishing the type, extent, and temporal relationship of exposure(s) to symptoms.
In patients with suspected HP, if the inciting antigen (IA) is thought to be related to an occupational exposure, the authors suggest considering the inclusion of an occupational medicine specialist and an environmental hygienist during the multidisciplinary diagnostic workup, especially when the source of exposure is obscure or unverified.
In patients with suspected HP, the authors suggest classifying patients based on the likelihood of an occupational or environmental inciting antigen exposure.
For patients with either newly diagnosed or a working diagnosis of HP, the authors suggest classifying the disease as fibrotic or nonfibrotic based on the presence or absence of fibrosis on high-resolution computed tomography (HRCT) of the chest.
In patients with suspected HP, if an IA exposure is identified and then completely avoided, the authors suggest using clinical improvement with antigen avoidance to support the diagnosis of HP, but not relying solely on the lack of clinical improvement with antigen avoidance to rule out the diagnosis of HP.
For patients with suspected HP, the authors suggest not relying solely on clinical improvement with medical therapy to confirm a diagnosis of HP or on the lack of clinical improvement with medical therapy alone to rule out the diagnosis of HP.
For patients with suspected HP, the authors suggest not relying solely on serum antigen-specific immunoglobulin G (IgG) or immunoglobulin A (IgA) testing to confirm or rule out the diagnosis of HP.
For patients with suspected HP, the authors suggest not performing antigen-specific inhalation challenge testing to support the diagnosis of HP.
For patients with suspected HP, the authors suggest not performing antigen-specific lymphocyte proliferation testing to support the diagnosis of HP.
For patients with suspected HP, the authors suggest the integration of HRCT findings characteristic of HP with clinical findings to support the diagnosis of HP, but not using the CT findings in isolation to make a definite diagnosis.
For patients with suspected HP, the authors suggest using a multidisciplinary discussion (MDD) for diagnostic decision-making.
For patients with suspected HP who have a compelling exposure history within the appropriate clinical context and a chest HRCT pattern typical for HP, the authors suggest not routinely using bronchoalveolar lavage (BAL) fluid analysis to confirm a diagnosis of HP.
In patients with suspected HP, the authors suggest considering histological lung biopsy for additional diagnostic evaluation when all available data such as clinical, laboratory, and radiologic findings along with bronchoscopic results do not yield a confident diagnosis and results may help guide management.
For patients with suspected HP, the authors suggest integrating biopsy findings with clinical and radiological findings to support the diagnosis of HP in the context of the MDD.
"Along with the physician's diagnosis, it is important for patients to understand their disease," says Dr. Fernández. "To assist those diagnosed with an interstitial lung disease, like HP, there are resources available on the CHEST Foundation website."
Reference:
"Diagnosis and Evaluation of Hypersensitivity Pneumonitis: CHEST Guideline and Expert Panel Report," is published in the journal CHEST.
DOI: https://journal.chestnet.org/article/S0012-3692(21)00686-3/fulltext