Classification of hypersensitivity pneumonitis: a hypothesis.

Area of Science:

• Pulmonary Medicine
• Immunology
• Radiology

Background:

• Hypersensitivity pneumonitis (HP) is typically classified as acute, subacute, or chronic.
• Current staging lacks clear diagnostic criteria, causing classification confusion.
• This study aimed to validate the existing HP classification against distinct clinical presentations.

Purpose of the Study:

• To determine if the current acute, subacute, and chronic classification of hypersensitivity pneumonitis (HP) reflects distinct clinical patient categories.
• To investigate the validity of established HP staging through data-driven cluster analysis.

Main Methods:

• A prospective, multicenter cohort study (HP Study) data was analyzed.
• Cluster analysis was employed to categorize 168 HP patients into distinct clinical groups.
• The identified clusters were compared against the traditional acute, subacute, and chronic HP classification.

Main Results:

• Cluster analysis identified two distinct patient groups (clusters) out of 168 participants.
• Cluster 1 (41 patients) presented with systemic symptoms and normal chest X-rays.
• Cluster 2 (127 patients) exhibited clubbing, hypoxemia, restrictive lung function, and fibrosis on HRCT, with significant differences (p < 0.0001).
• There was substantial disagreement between the cluster analysis findings and the conventional HP classification.

Conclusions:

• The current classification of hypersensitivity pneumonitis (HP) into acute, subacute, and chronic stages is not supported by this clinical data analysis.
• The subacute stage of HP is particularly challenging to define and differentiate based on clinical features.