The similarity of the physical sign frequencies of bovine spongiform encephalopathy and selected differential diagnoses.

This paper describes a method which enables the similarity of diseases based upon their physical sign frequencies to be defined relative to bovine spongiform encephalopathy (BSE). The means of the absolute differences between the sign frequencies of BSE and the differential diagnoses were used as measure of similarity. Four sets of signs were compared. The most useful quantitative measurement of difference between the diseases was achieved when only the variant signs were used. Diseases that have a high similarity to BSE when the variant signs are compared are more likely to have case presentations that approximate to those found in BSE. These are the diseases that are most likely to be confused with BSE by clinicians. Previously published BSE differential diagnoses from clinical opinion and brain histopathology are reported and compared to the diseases used in this study.