OBJECTIVE INTERPRETATION OF BOVINE CLINICAL BIOCHEMISTRY DATA - APPLICATION OF BAYES LAW TO A DATABASE MODEL

With the advent of animal-side biochemistry analysers in veterinary pr actice, the requirement for ready access to reliable means for interpr etation of the results is of increasing importance. At the University of Glasgow Veterinary School (GUVS), a large computerised hospital dat abase containing extensive clinical, laboratory, and pathological info rmation has been maintained. A retrospective study was undertaken to i nvestigate plasma biochemistry results and corresponding post mortem d iagnosis data from 754 unwell cattle which had presented to GUVS over the study period. Initial analysis of the clinical biochemistry data f rom this unwell population revealed that the parameters did not follow a normal distribution. This finding suggested that the accepted refer ence range method for the interpretation of clinical biochemistry data may provide limited information about the unwell animal. By applying a combination of percentile analysis and conditional probability techn iques to the hospital data, the development of a means of clinical bio chemistry interpretation was developed whereby a clinician could deter mine whether a value was abnormal, the degree of abnormality, and the most likely associated diseases. For example, a urea value of 30 mmol/ l lay within the top 5% of results, and one of the most common disease s associated with this urea value was pyelonephritis. Furthermore, a B ayesian approach allowed the quantification of the relationship betwee n any plasma biochemistry value and disease through the generation of a ratio termed the 'biochemical factor'. Using the same example, given a urea value of 30 mmol/l, pyelonephritis was eight times more likely than before any biochemistry information was known. The results from the study were used to form the basis of a software system which may u ltimately be used by the clinician to aid in the recognition, treatmen t and prevention of disease in the veterinary domain. (C) 1998 Elsevie r Science B.V.