Diagnostic reliability of clinical signs in cows with suspected bovine spongiform encephalopathy.

The clinical findings in 50 cows with suspected and subsequently confirmed bovine spongiform encephalopathy (BSE) (group A) were compared with the clinical signs in 22 cows with suspected BSE, but with no histological evidence of the disease (group B). The chi-square test for association was used to compare the frequencies with which diagnostic signs or combinations of signs, were positive in the cows of groups A and B. When the frequency of a sign differed significantly, its sensitivity, specificity, efficiency and positive and negative predictive values were calculated. With respect to changes in behaviour the cows in group A more frequently showed increased excitability, nervous ear and eye movements, increased salivation and increased licking of the muzzle than the cows of group B. With respect to changes in sensitivity the cows in group A were more frequently hypersensitive to touch, noise and light than the cows of group B. With respect to changes in locomotion the cows in group A were more frequently ataxic than the cows in group B.