From the Guidelines
Steroid therapy should be temporarily discontinued before testing for hypersensitivity pneumonitis to avoid false-negative results, as recommended by the most recent guidelines 1.
Recommendation Details
The decision to discontinue steroid therapy is based on the understanding that steroids suppress the inflammatory response being measured in diagnostic tests for hypersensitivity pneumonitis.
- Systemic corticosteroids, such as prednisone, should be stopped at least 2 weeks prior to diagnostic testing, including bronchoscopy with bronchoalveolar lavage (BAL), lung biopsy, or specific antigen challenge tests.
- For patients on inhaled steroids, these should be discontinued 48-72 hours before testing if possible.
- If a patient cannot safely discontinue steroids due to severe symptoms or other medical conditions, this should be clearly documented and considered when interpreting test results.
Rationale
The rationale behind this recommendation is that steroids can reduce the lymphocytosis in BAL fluid and mask the characteristic histopathological findings in lung tissue samples, potentially leading to false-negative results 1. After testing is complete, steroid therapy can be resumed as needed for treatment. For patients with suspected acute hypersensitivity pneumonitis who require immediate treatment, diagnostic testing should ideally be performed before initiating steroid therapy whenever the clinical situation allows, as emphasized in the guidelines 1.
From the Research
Hypersensitivity Pneumonitis Testing on Steroids
- The use of systemic steroids in the treatment of hypersensitivity pneumonitis (HP) has been studied in various research papers 2, 3, 4.
- According to a study published in 2013, systemic steroids are of value for subacute and chronic forms of HP, but do not influence long-term outcome 2.
- A 2020 study found that prednisone can reverse lung function declines in HP patients without established fibrosis, and second-line immunosuppressants like azathioprine and mycophenolate mofetil have a steroid-sparing effect and improve DLCO 3.
- Another study published in 2017 compared the outcomes of immunosuppressive therapy in chronic HP and found that the use of azathioprine or mycophenolate mofetil with prednisone reduces adverse events and lung function decline, but does not improve transplant-free survival 4.
- The diagnosis of HP requires a detailed history, measurement of environmental exposure, pulmonary function tests, imaging, detection of serum specific antibodies, broncho-alveolar lavage, antigen-induced lymphocyte proliferation, environmental or laboratory-controlled inhalation challenge, and lung biopsy 2, 5.
- Complete antigen avoidance is the best therapeutic measure, although it can be difficult to achieve in some cases 2, 5.
Steroid Treatment Outcomes
- A study published in 2020 found that leflunomide treatment improved pulmonary function in non-fibrotic chronic HP patients, with an increase in FVC of 8.3% and DLCO of 4.8% 3.
- However, patients with fibrotic chronic HP did not improve with leflunomide treatment 3.
- The use of steroids in HP treatment has been associated with significant gastrointestinal and other adverse effects, leading to discontinuation of therapy in some cases 3, 4.
Immunologic Response
- The immunologic response in HP includes activated macrophages and CD8+ cytotoxic lymphocytes, and bronchoalveolar lavage fluid reveals marked lymphocytosis with a ratio of CD4+ to CD8+ cells of <1 6.
- Activated macrophages have increased expression of CD80/CD86, and T cells have increased expression of its counter-ligand, CD28, evidence for heightened antigen presentation 6.