Vitiligo in a cow apparently associated with hepatosis

I am concerned with the claims about the interpretation of the clinical pathological results in a recent letter published in the New Zealand Veterinary Journal (Yeruham et al., 1998). The authors present serum biochemical values with which they claim to diagnose hepatosis. These values are only just outside the reference ranges, and do not in my opinion prove hepatosis. Reference ranges usually cover 95% of normal animals from a population. This means that 5% of normal animals will lie just outside the reference range, either above or below (Duncan et al., 1994). These animals will, however, be completely normal. The alterations in analytes quoted in this letter are so small that they may very well lie within these normal categories. The authors have measured serum alanine aminotransferase (ALT) concentrations which are not useful for diagnosing large animal liver disease (Duncan et al., 1994). In fact, in cattle they may…