Evaluation of Histogel- and Gelfoam-embedded bronchoalveolar lavage and transtracheal wash fluids compared with cytocentrifuged and sediment smear preparations.

Abstract

BACKGROUND: Storage and temperature significantly impact bronchoalveolar lavage fluid (BALF) analysis, and shipment of samples to diagnostic laboratories is often necessary. Alternative sample preparation methods could limit storage and temperature effects. OBJECTIVES: This study aimed to determine if airway wash samples that were fixed in formalin after being embedded in Histogel or Gelfoam gave comparable results to fresh cytocentrifuged or sediment smear preparations for the evaluation of cell morphology. METHODS: Eleven bronchoalveolar lavage and 3 transtracheal wash fluids were available, including 8 canine, 1 feline, and 5 equine samples. Cytocentrifuged and sediment smear preparations were prepared for routine analysis. Airway fluids were reserved for further evaluation. Total nucleated cell counts (TNCCs) were determined using a hemocytometer. The remaining fluid was used for Histogel and Gelfoam preparations. Each preparation was analyzed by a single board-certified clinical pathologist and assigned cellularity (1-3) and morphology scores (1-4). RESULTS: Cellularity and morphology were significantly worse for the sediment smear, Histogel, and Gelfoam preparations compared with the cytocentrifuged preparations. The Gelfoam preparations had significantly worse cellularity scores than all other methods. Cellularity scores for sediment smears and Histogel preparations were significantly correlated with TNCCs. CONCLUSIONS: TNCCs impacted the cellularity of the sediment smears and Histogel preparations. Cytocentrifuged preparations resulted in the best cellularity and morphology and are, therefore, recommended whenever possible. Neither the Histogel nor the Gelfoam methods demonstrated any advantage over sediment smear preparations, and both performed poorly when compared with cytocentrifuged preparations. Therefore, we do not recommend the use of these methods.