Valutazione dell’accuratezza diagnostica di un boroscopio flessibile per la diagnosi della dermatite digitale in sala di mungitura.

Evaluation of diagnostic accuracy of flexible borescope diagnosing digital dermatitis in milking parlor.

Abstract

Digital dermatitis causes lameness, discomfort, and economic losses worldwide. The test considered the ‘gold standard’ for diagnosis of digital dermatitis is the visual inspection of the feet into a trimming chute. However, this test is challenging to perform in daily operations. For this reason, several alternative methods to diagnose digital dermatitis in the milking parlor have been explored in the last years. The use of a rigid borescope was one of them but its use has been limited because of its laborious use in the milking parlor and its high cost. Several and affordable models of flexible borescope are now available on the market. Our study objective was to quantify the accuracy of a flexible borescope for diagnosing digital dermatitis in a milking parlor. The study was conducted in a commercial free-stall herd milking approximately 200 cows. The borescope evaluation of hind feet was performed in the milking parlor 24-48 hours before the routine preventive hoof trimming. The same observer was used to diagnose the disease. The lesions at both evaluations were scored using the classification described by Döpfer and modified by Berry (2001). 

Data were analyzed using two statistical approaches. In the first one, data were dichotomized as digital dermatitis lesions (M1, M2, M3, M4, M4.1) vs. no lesions (M0). In the second one, data were dichotomized as active lesions of digital dermatitis (M1, M2, M4.1) vs. chronic lesions/no lesions of digital dermatitis (M3, M4, M0). Sensitivity, specificity, and predictive values of both models were computed. Data from 870 hind feet were analyzed. Using the first approach, sensivity, specificity, positive and negative values were 64% (95%C.I.: 57%-69%), 91% (95%C.I.: 88%-93%), 97% (95%C.I.: 91%-99%) and 80% (95%C.I.: 78%-83%), respectively. Using the second approach, the values were 39% (95%C.I.: 32%-45%), 99% (95%C.I.: 98%-100%), 97% (95%C.I.: 91%-99%) and 80% (95%C.I: 77%-83%), respectively.

Based on these results, it was concluded that a flexible borescope can be used to diagnose the digital dermatitis lesions in the milking parlor. However, the ability of this test to diagnose active lesions of digital dermatitis appears to be limited. This means that it could result in an underestimation of the true prevalence of active lesions compared with the gold standard technique.