What is the best management approach for a patient with suspected hypersensitivity pneumonitis (HP), reduced Diffusing Capacity of the Lung for Carbon Monoxide (DLCO), and symptoms of chronic cough and potential bronchospasm while waiting for a High-Resolution Computed Tomography (HRCT) scan?

Management While Awaiting HRCT in Suspected Hypersensitivity Pneumonitis

For a patient with suspected hypersensitivity pneumonitis, reduced DLCO, chronic cough, and potential bronchospasm awaiting HRCT, immediately initiate a systematic exposure assessment and begin empiric bronchodilator therapy while avoiding corticosteroids until diagnostic testing is complete. 1, 2

Immediate Exposure Assessment

The single most critical intervention is identifying and removing the inciting antigen, as this alone can lead to complete disease resolution in non-fibrotic cases. 2, 3

• Conduct detailed questioning about occupational exposures (metalworking fluids, agricultural dusts, industrial chemicals), household exposures (mold, water damage, humidifiers, hot tubs, birds, feather bedding), and hobbies (woodworking, pottery) 1, 3
• If an exposure is identified, implement immediate avoidance measures before HRCT results, as antigen removal is the cornerstone of treatment and delays worsen outcomes 2, 3
• Consider serum IgG testing against suspected antigens if exposure history is unclear, though positive results only indicate exposure, not disease 3

Symptomatic Management of Cough and Bronchospasm

Address the chronic cough by treating potential bronchospasm and excluding common comorbid conditions rather than waiting for definitive diagnosis. 1, 2

• Trial inhaled bronchodilators (short-acting beta-agonists and/or anticholinergics) for suspected bronchospasm, as small airway disease is a hallmark feature of HP 1, 2
• Systematically evaluate and treat upper airway cough syndrome (UACS), asthma, and gastroesophageal reflux disease (GERD), as these commonly coexist with interstitial lung disease and contribute to chronic cough 1, 2
• For GERD evaluation, trial high-dose proton pump inhibitor therapy, recognizing that response may take 2 weeks to several months 1

Critical Management Pitfalls

Do not initiate corticosteroids empirically before completing diagnostic evaluation, as this can obscure histopathological findings and complicate diagnosis. 1

• Corticosteroids alter BAL lymphocyte counts and histopathological features, potentially preventing accurate diagnosis if bronchoscopy becomes necessary 1
• The diagnostic triad of exposure history, typical HRCT pattern, and BAL lymphocytosis ≥30% provides high-confidence diagnosis, and premature steroid use compromises two of these three elements 1, 3

Pulmonary Function Monitoring

Obtain baseline spirometry with DLCO measurement if not already done, as this establishes disease severity and provides a reference for monitoring progression. 2

• The reduced DLCO already documented suggests significant disease activity and helps stratify severity 1, 2
• Serial pulmonary function testing every 3-6 months tracks disease progression, with declining FVC and DLCO indicating active disease requiring intervention 1, 2

Expedite Diagnostic Completion

Prioritize obtaining HRCT with proper technique (submillimetric collimation, inspiratory and expiratory acquisitions) and ensure review by a thoracic radiologist experienced in interstitial lung disease. 1, 2

• HRCT is the single most important diagnostic test and will determine whether the patient has non-fibrotic versus fibrotic HP, which fundamentally changes prognosis and treatment approach 1, 2, 4
• Fibrotic HP carries 4.35 times increased mortality risk compared to non-fibrotic HP, making this distinction urgent 2
• Look for characteristic findings including profuse centrilobular nodules, mosaic attenuation with air-trapping on expiratory images, and three-density sign for non-fibrotic HP 1, 3, 4

Prepare for Multidisciplinary Discussion

Arrange for multidisciplinary discussion involving pulmonologist, thoracic radiologist, and potentially pathologist once HRCT results are available, as this integration is essential for confident diagnosis. 1, 3

• If HRCT shows typical HP pattern and exposure is identified, BAL with lymphocyte analysis (threshold ≥30%) may provide high-confidence diagnosis without need for biopsy 1, 3
• If diagnostic confidence remains moderate or low after HRCT, bronchoscopy with BAL and transbronchial biopsy should be considered, particularly for suspected non-fibrotic HP 1

Avoid Premature Treatment Decisions

The critical error is initiating immunosuppression before establishing whether the patient has non-fibrotic versus fibrotic disease, as recent evidence shows immunosuppression does not prevent decline in fibrotic HP and may delay appropriate antifibrotic therapy 5, 6. Patients with extensive ground glass may improve with or without immunosuppression, while those with established fibrosis (>20%) continue declining despite immunosuppressive treatment 5, 6.