"Evaluation of the reliability of the cytological examination of tracheobronchial secretions and bronchoalveolar lavage for the diagnostics of equine asthma" Equine asthma is a common chronic respiratory disease that can affect horses of all ages. In addition to a clinical examination of the respiratory tract, the cytological examination of tracheobronchial secretions (TBS) and bronchoalveolar lavage (BAL) plays an important role in the diagnosis of equine asthma. The aim of this study was to compare cytological results and tentative diagnoses within and between different laboratories to assess the reliability of cytological examination of TBS and BAL as a diagnostic tool for equine asthma. The hypotheses of this study were that, in an intra- and inter-individual comparison of cytological results from TBS and BAL within and between multiple laboratories, there would be little to no variance in the results and tentative diagnoses, and that cytology could be used as a reliable criterion for respiratory tract diagnostics. The study population consisted of 15 horses presented for evaluation of respiratory symptoms. Initially, respiratory tract examinations were performed on all horses, and the findings from the clinical, endoscopic, and cytological examinations were used for the final diagnosis in the clinic. This allowed the categorization of the study horses into five healthy horses, five horses with mild to moderate equine asthma, and five horses with severe equine asthma. Air-dried smears of TBS and BAL from the study horses were then sent to four external laboratories. In addition, the smears were evaluated by two examiners from the equine clinic. Each laboratory and examiner analyzed the samples of the same horse twice in a double-blind manner. The results from the external laboratories showed marked differences in the reported differential cell counts and cytological evaluation of TBS and BAL. Some laboratories provided semi-quantitative data, while others provided percentage values for differential cell counts. To allow for inter-individual variance in the results from different laboratories, a standardized scoring system for cytological assessment of TBS and BAL was developed. When comparing the intra-individual agreement of results within the external laboratories and examiners from the clinic, it was confirmed that there was good agreement in the results for neutrophil granulocytes in BAL and TBS among most laboratories (ICC 0.75, weighted kappa 0.6). Moreover, laboratories that provided percentage values for differential cell counts also showed good agreement for macrophages, lymphocytes, eosinophilic granulocytes, and mast cells. The semi-quantitative data yielded less reproducibility of results for the cell types of differential cell counts among different laboratories. Thus, the method of cytological evaluation influenced the reproducibility of the results. Overall, the results varied less for BAL, indicating that this sample type is recommended for more valid cytological results. When comparing results between all laboratories, good reproducibility was also achieved for neutrophil granulocytes in BAL and TBS (Krippendorff's alpha 0.7). This cell type had the greatest impact on cytological diagnosis. The results for all other cell types of differential cell counts varied more between the laboratories. Lung-healthy horses were frequently diagnosed with mild to moderate equine asthma by the external laboratories. In diseased horses, equine asthma was mostly diagnosed, although the severity of the disease varied between and within the laboratories. One laboratory additionally diagnosed bacterial bronchitis in some horses. The hypothesis that TBS and BAL cytology can be used as a reliable criterion for respiratory tract diagnostics and that it plays an important role in the diagnosis needs to be restricted due to some intra- and inter-individual differences in cytological results and variations in tentative diagnoses between and within the laboratories. These differences can be attributed, in part, to the different evaluation methods used for the samples. Therefore, it can be concluded that cytological examination should only be used as a small part of the final diagnosis, and clinical symptoms should have the greatest influence on the diagnosis and subsequent therapy. Without detailed information on clinical symptoms and medical history, valid cytological diagnoses are limited. The combination of all findings should serve as the gold standard for diagnosis. As a recommendation, the same laboratory should always be used for cytological evaluation, especially in follow-up examinations, to obtain valid cytological results. Additionally, there is a need for a standardized cytological assessment of TBS and BAL to enable comparison of results between different laboratories. The scoring system developed in this study can serve as a suggestion for standardized evaluation and could demonstrate its validity in further studies.weiterlesen