Example of early disease with mild flattening of the diaphragm<unk>  is often diagnosed based on the symptoms of obstructive lung disease following lung injury. The definitive diagnosis is through biopsy, but due to the variable distribution of lesions, leading to falsely negative tests, and invasive nature of this procedure it is often not performed. Several tests are often needed to diagnose<unk> , including spirometry, diffusing capacity of the lung tests (DLCO), lung volume tests, chest X-rays, high-resolution CT (HRCT), and lung biopsy. Pulmonary function testing Spirometry tests usually show an obstructive pattern and is the most common presentation. A slightly reduced to normal forced vital capacity (FVC), and a reduced FEV1 to FVC ratio and forced expiratory volume (FEV) with little to no correction with the use of bronchodialators are common findings. Lung volume tests may show hyperinflation (excessive air in lungs caused by air trapping). Diffusing capacity of the lung (DLCO) tests are usually normal; people with early-stage OB are more likely to have normal DLCO. FEV1 (forced expiratory volume in 1 second) should be above 80% of predicted values to be considered normal.<unk>  reduces this to between 16% and 21%. Medical imaging Early in the disease chest radiography is typically normal but may show hyperinflation. As the disease progresses a reticular pattern with thickening of airway walls may be present. HRCT can also show air trapping when the person being scanned breathes out completely; it can also show thickening in the airway and haziness in the lungs. A common finding on HRCT is patchy areas of decreased lung density, signifying reduced vascular caliber and air trapping. This pattern is often described as a "mosaic pattern", and may indicate<unk> . Lung biopsy Transthoracic lung biopsies are preferable for diagnosis of constrictive<unk>  compared to transbronchial biopsies; regardless of the type of biopsy, a diagnosis may only be achieved by examination of multiple samples. Transthoracic biopsies are preferred over transbronchial due to the heterogeneity and distribution of the lesions. OB can be further classified into two categories: constrictive or proliferative. The constrictive pattern is demonstrated by peribronchiolar cellular infiltrates which eventually causes small airway damage and leads to subepithelial fibrosis. The bronchial muscle can eventually become fibrosed which can be identified with trichrome staining. In regards to proliferative disease, intraluminal buds called "Masson<unk> dies" fill the lumen, which results in bronchiolar plugging. Often people with proliferative disease will show butterfly wing-like appearance under microscopy. One key determinate that can be seen on biopsy to differentiate constrictive from proliferative disease is the extent of lesions.<unk> th lesions are localized from the small bronchi to the membranous bronchi, but in constrictive disease, the lesions are intermittent while proliferative disease has a continuous distribution. Differential diagnosis Other conditions that can present similarly include chronic obstructive pulmonary disease, asthma, bronchiectasis, hypersensitivity pneumonitis, and pneumonia.
Bronchiolitis obliterans
Asthma
Diffuse panbronchiolitis
Emphysema
Mineral dust airway disease
Eosinophilic bronchitis
Plastic bronchitis
Pulmonary hyalinizing granuloma