Introduction to Laboratory Profiling

INTRODUCTION TO LABORATORY PROFILING

Biochemical profiling may be defined as the use of multiple blood chemistry determinations to assess the health status of various organ systems simultaneously. Biochemical profiling rapidly has become a major diagnostic aid for the practicing veterinarian for several reasons. First, a more educated clientele has come to expect increased diagnostic sophistication. Secondly, the advent of high-volume clinical pathology laboratories has resulted in low prices that make profiling in veterinary practice feasible and convenient. In addition, improved technology has resulted in the development of procedures that can be used to obtain accurate analyses on microsamples of serum. Such procedures offer obvious advantages to veterinarians, who in the past were hindered by requirements for large sample size.

Although biochemical profiling offers exciting potential, it is not a panacea. Since standard chemical screens provide 12 to 30 test results, interpretation of data may be extremely complex. Interpretation is often clouded by the fact that perfectly normal animals may have, indeed, are expected to have, an occasional abnormal test result. It is estimated that in a panel of 12 chemistry tests, approximately 46% of all normal subjects will have at least one abnormal test result. Such abnormalities do not reflect inaccuracies in laboratory test procedures but rather the way in which reference (or normal) values are determined. In order to establish the “normal range” for a given test, the procedure is performed on samples from a large population of clinically normal individuals. A mean and a standard deviation are determined. The reference values are then defined as those values falling within two standard deviations above and below the mean. Since two standard deviations above and below the mean only include 95% of all determined values, 5% of the values obtained from a normal population are by this definition abnormal. […]