Endoscopic scoring of mucus quantity and quality: observer and horse variance and relationship to inflammation, mucus viscoelasticity and volume.
Authors: Gerber V, Straub R, Marti E, Hauptman J, Herholz C, King M, Imhof A, Tahon L, Robinson N E
Journal: Equine veterinary journal
Summary
# Editorial Summary Endoscopic examination of airway mucus is routine in equine practice, yet the reliability and clinical relevance of visual scoring systems had never been rigorously validated. Gerber and colleagues evaluated how consistently different observers could score mucus quantity, viscosity, colour and location in tracheal secretions, and whether these scores correlated with objective measures of inflammation, mucus volume and viscoelasticity. Using multiple observers assessing the same horses over time, they found that mucus accumulation scoring demonstrated excellent reproducibility between observers and strong correlation with both measured mucus volume and neutrophil counts in secretions—making it a genuinely useful clinical indicator of airway inflammation. However, visual assessment of mucus viscosity, colour and localisation proved highly inconsistent between observers and did not correlate with laboratory measurements of mucus viscoelasticity, significantly limiting their diagnostic value. The practical takeaway is clear: practitioners can confidently use endoscopic accumulation scoring as a reliable measure of tracheal mucus burden and inflammatory status, but should not rely on subjective impressions of mucus appearance or consistency, which introduce substantial observer bias and lack objective validation.
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Practical Takeaways
- •Use endoscopic mucus accumulation scoring as a reliable, reproducible clinical tool for assessing tracheal mucus burden and airway inflammation in horses
- •Do not rely on subjective scoring of mucus viscosity, colour, or location as these parameters show high observer variability and poor correlation with measured properties
- •Recognize that mucus location matters: dorsal tracheal mucus is stiffer and may behave differently than ventral accumulations
Key Findings
- •Endoscopic mucus accumulation scoring demonstrated excellent interobserver agreement and moderate horse-related variance
- •Mucus accumulation scores correlated well with measured tracheal volumes and neutrophilic airway inflammation
- •Scores for mucus viscosity, colour, and localisation showed high observer-related variance and poor reliability
- •Dorsally-localised mucus showed 2-fold higher measured viscoelasticity than ventrally-localised samples