Pulmonary Fibrosis: Classification

For a diagnosis of idiopathic pulmonary pulmonary fibrosis (IPF), either criteria 1 and 2 or 1 and 3 must be met:

  1. Interstitial lung disease (ILD) or diffuse parenchymal lung disease (DPLD) of known cause (e.g., noxious exposure, collagenoses, other systemic diseases, drug-induced ILD, etc.) must be excluded.
  2. In high-resolution computed tomography (HRCT), a UIP pattern (usual interstitial pneumonia: honeycomb pattern with or without traction bronchiectasis (form of bronchiectasis/dilatation of the alveoli, in which there is dilatation of the bronchi or bronchioles due to pulmonary fibrosis or distorted lung parenchyma (lung tissue), etc.) must be present.
  3. Presence of specific combinations of HRCT and histology results.

Combination of HRCT and histopathology in the diagnosis of IPF [S2k guideline].

Suspicion of IPF Histopathology
UIP probably UIP indeterminate pattern Alternative diagnosis
HRCT pattern UIP IPF IPF IPF no IPF
probably UIP IPF IPF IPF(probable)* No IPF
Indeterminate pattern IPF IPF(probable)* and classifiableILD* * No IPF
Alternative diagnosis IPF(probable)* /no IPF no IPF no IPF No IPF

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* The diagnosis of IPF is likely if any of the following characteristics apply after exclusion of alternative causes:

  • Moderate to severe traction bronchiectasis and bronchioloctasis (defined as mild traction bronchiectasis in four or more lobes of the lung, including the lingula, or moderate to severe traction bronchiectasis in two or more lobes) in a man over 50 years of age or in a woman over 60 years of age
  • Extensive (>30%) reticulations on HRCT and age >70 years.
  • Increased neutrophil granulocytes and/or absence of lymphocytes in bronchoalveolar lavage (BAL; sample collection method used during bronchoscopy (lung examination)).
  • Multidisciplinary case discussion agrees on a definite diagnosis of IPF.

* * Undetermined pattern

  • Without a conclusive biopsy, IPF is unlikely.
  • With meaningful biopsy, reclassification to a more specific diagnosis can be made through multidisciplinary case discussion and/or additional consultation