Effect of Dithiothreitol on the Differential Cellcount of Equine Tracheal Wash Aspirates

Potts, V., Pirie, S., McGorum, B., McGregor, G., Drumond, D. and Moss, S. (2019) Effect of Dithiothreitol on the Differential Cellcount of Equine Tracheal Wash Aspirates. 11th Annual European College of Equine Internal Medicine Congress, Ghent, Belgium, 9-10 Nov 2018. (doi: 10.1111/jvim.15447)

Abstract

Analysis of tracheal secretions is a commonly applied diagnostic modality in the investigation of equine lower airway disease. In human respiratory medicine, the addition of a mucolytic agent following col-lection has been shown to increase diagnostic sensitivity, total cell recovery and the quality of cytospin preparations. We hypothesised that the addition of the mucolytic Dithiothreitol (DTT) to equine tracheal wash samples would (a) reduce background mucus superimposition, (b) improve the “readability” of cytospin preparations and (c)significantly alter neutrophil differential ratios. Fifty nine tracheal wash samples were collected from forty two horses presenting either with clinical signs consistent with, or for routine screening for lower airway inflammation. Prior to processing, one sample aliquot was treated with an equal volume of 0.1% DTT and the paired aliquot left untreated. Samples were subsequently cytospun and stained using May-Grünwald Giemsa. Differential cell counts and slide quality scores were calculated(1). Paired data were compared (Wilcoxon Rank test)and analysed for agreement (Bland-Altman plots). Significant airway inflammation was assumed beyond a threshold of 20% neutrophils. DTT treatment significantly reduced back-ground mucus staining and consequently improved “readability” of the preparations. Regarding neutrophil ratios, there was no significant difference, and good agreement, between treated and untreated samples. Dis-counting cases with cytological evidence of bacterial infection, addition of DTT did not significantly (Fishers exact ;P= 0.17) alter the categorisation of cases based on the 20% threshold. Based on these results, addition of DTT facilitates cytological examination of tracheal wash cytospin preparations without altering the differential neutrophil percentage.

• Item Type: Conference or Workshop Item
• Additional Information: Abstract published in Journal of Veterinary Internal Medicine 2019; 33(3):1554-1554
• Status: Published
• Refereed: No
• Glasgow Author(s) Enlighten ID: de Boer, Mrs Valerie
• Authors: Potts, V., Pirie, S., McGorum, B., McGregor, G., Drumond, D., and Moss, S.
• College/School: College of Medical Veterinary and Life Sciences > School of Biodiversity, One Health & Veterinary Medicine