Bronchoalveolar lavage fluid cytology and airway hyper-reactivity in clinically normal horses.

This research paper investigates the relationship between bronchoalveolar lavage fluid (BALF) cytology and lung function tests in a group of healthy horses, specifically focusing on their response to an introduced histamine stimulant. The research findings indicate that there’s no direct correlation between signs of airway inflammation seen in BALF cytology and hyper-reactive airway responses.

Methodology

• In this cross-sectional study, a total of 33 clinically normal adult horses underwent lung function tests and histamine bronchoprovocation (HBP), a procedure designed to provoke a response in the airways. The HBP evaluations were carried out using a commercial flowmetric plethysmography system.
• A few days post the HBP tests (1-5 days), bronchoalveolar lavage (BAL) was performed on the horses. BAL is a technique where a fluid is introduced, and then removed, from the bronchi (a part of the lung), with the latter containing cells and microbes which can be analyzed (BALF cytology).
• Using statistical analysis, the researchers examined correlations between the concentration of cells in the BALF, percentages of inflammatory cells and their categorization, and the airway hyper-reactivity (AHR) seen in pulmonary function tests.

Results

• The study found that 52% of the horses showed airway hyper-reactivity (AHR) to histamine.
• According to the present definitions, 42% of the horses’ BALF cytology was consistent with inflammatory airway disease. Among the horses with inflammatory disease, about half showed mastocytic or eosinophilic responses.
• However, no correlation was found between the total inflammatory cell counts or their relative percentage and AHR.
• No statistical association was established between the categorization of inflammatory cells in BALF and AHR.

Conclusions

• The research concluded that there is no direct association between cytological evidence of airway inflammation and AHR in clinically healthy horses.
• It suggests that determining the presence of, and measuring, inflammatory cell mediators in BALF might more accurately reflect AHR.
• The researchers also suggest that ‘normal’ values for cell proportions in BALF might vary among different horse populations, hence regional reference ranges may be more appropriate.