Diagnostic accuracy of swine echinococcosis cytopathological tests and challenges for a differential diagnosis: slaughterhouse data

Summary Echinococcosis disease shows clinical signs similar to many diseases. Hence we report cases that need to be confirmed using appropriate tests. A confirmatory study has been conducted to assess the accuracy of two cytopathological tests, with the histopathology test as the reference standard. The first cytopathological test evaluates the Ziehl Neelsen staining with an epifluorescence microscope (cytopath 1). The second cytopathological test uses the same staining followed by a transmitted light microscope examination (cytopath 2). Of a total of 2524 inspected pigs, 101 suspected cases of echinococcosis were detected, of which 67 were found positive with the two cytopathological tests and the histopathological one. The specificity of cytopath 1 (100 % [95 % CI 100 – 100]) and cytopath 2 (100 % [95 % CI 100;100]) were similar, as well as their respective positive predictive values: 100 % [95 % CI 100 – 100] vs. 100 % [95 % CI 100 – 100]. The sensitivity of cytopath 1 is 79.66 % [95 % CI 69.39 – 89.93], while cytopath 2 equals 66.10 % [95 % CI 54.02 – 78.18]. The difference in sensitivity of both tests was not significant. Negative predictive values found for cytopath 1, and cytopath 2 were 40 [95 % CI 18.53 – 61.47] and 28.57 [95 % CI 11.84 – 45.3], leading to the Generalized Estimating Equations (GEE) Model estimate for an odds ratio of 1.4 [95 % CI 0.41 – 5.2], p = 0.06. Cytopath 1 and cytopath 2 are equivalent in terms of specificity (100 % [95 % CI 100 – 100] vs. 100 % [95 % CI 100;100]) and positive predictive value (100 % [95 % CI 100 – 100]. Cytopath 1 is more sensitive than cytopath 2 but not significant (79.66 % [ 95 % CI 69.39 – 89.93] vs. 66.10 % [95 % CI 54.02 – 78.18]). However, the negative predictive value of cytopath 1 is better than that of cytopath 2: 40 % [95 % CI 18.53 – 61.47] vs. 28.57 % [95 % CI 11.84 – 45.3].