From the Guidelines
Bronchial lavage findings in organizing pneumonia typically show a mixed cellular pattern with increased lymphocytes, neutrophils, and eosinophils, along with a decreased CD4/CD8 ratio, as supported by the most recent and highest quality study available 1. The fluid often demonstrates increased total cell counts with a reduction in the percentage of macrophages compared to normal lavage samples.
- Key characteristics of bronchial lavage findings in organizing pneumonia include:
- Increased lymphocytes (20-40%)
- Increased neutrophils (10-20%)
- Increased eosinophils (5-10%)
- Decreased CD4/CD8 ratio
- Presence of foamy macrophages, though not specific to organizing pneumonia
- Negative for malignant cells and infectious organisms, helping to differentiate from infections and malignancies According to the American Thoracic Society clinical practice guideline 1, a minimal volume of 5 ml of a pooled BAL sample is needed for BAL cellular analysis, and the optimal volume is 10 to 20 ml.
- The guideline also states that BAL cell differential counts with greater than 15% lymphocytes, greater than 3% neutrophils, greater than 1% eosinophils, and greater than 0.5% mast cells represent a lymphocytic cellular pattern, neutrophilic cellular pattern, eosinophilic cellular pattern, and mastocytosis, respectively. While these findings support a diagnosis of organizing pneumonia, they are not pathognomonic, and the definitive diagnosis typically requires histological confirmation through lung biopsy showing the characteristic pattern of intra-alveolar buds of granulation tissue (Masson bodies) within alveolar ducts and adjacent alveoli, as described in the British Thoracic Society guideline 1. The lavage findings reflect the underlying immunological and inflammatory processes occurring in organizing pneumonia, where an initial lung injury triggers an abnormal healing response characterized by fibroblast proliferation and matrix deposition within the alveolar spaces.
From the Research
Bronchial Lavage Findings in Organising Pneumonia
The bronchial lavage findings in organising pneumonia are characterized by several features, including:
- A colorful cell differential with an increase in all cell types, most markedly in lymphocytes, and more moderately in neutrophils, eosinophils, and mast cells, as well as the presence of foamy macrophages and, occasionally, of plasma cells 2
- A decreased CD4/CD8 ratio 2
- A normal percentage of CD57+ cells 2
- An increase in activated T-cells in terms of human leucocyte antigen-DR (HLA-DR) expression, and occasionally also interleukin-2 receptor (CD25) expression 2
Comparison with Other Interstitial Lung Diseases
The findings in organising pneumonia are most similar to those in extrinsic allergic alveolitis (EAA), except for the CD25 expression, which is always normal, and the CD57+ cells, which are increased in EAA 2
- The increase in lymphocytes discriminates best between organising pneumonia and idiopathic pulmonary fibrosis (IPF) 2
- The eosinophils are significantly higher in chronic eosinophilic pneumonia (CEP) than in organising pneumonia, with little overlap 2
Clinical Implications
The bronchial lavage findings in organising pneumonia may be of value in distinguishing between organising pneumonia and other interstitial lung diseases 2
- However, the diagnosis of organising pneumonia requires histology, and open lung biopsy or video-assisted thoracoscopy is usually required to obtain specimens large enough for the diagnosis to be made 3