Page 207 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

174 SECTION | I General

VetBooks.ir REASONS FOR CONDUCTING case, may not be admissible in court because of insuffi-
cient documentation supporting authenticity. Other labo-
TOXICOLOGY ANALYSES
ratories may provide such documentation.
Toxicology has been defined as “the scientific study of
Veterinary diagnostic laboratories normally have some
adverse effects of chemicals on living organisms.” Eaton A government support to assist in the clinical diagnosis of
toxicologist is one trained to examine the nature of those diseased animals. Such analyses are normally aimed at
effects and assess the probability of their occurrence. Ibid assisting in the determination of whether an animal may,
Exposure, dose response, and variability of that response or may not, have been exposed to a particular chemical,
are fundamental principles in the science of toxicology. Ibid and if so, whether the animal has, or has not, experienced
A showing that the toxicologist offered as an expert wit- a toxicosis as a result of that exposure. These chemical
ness has applied these fundamental principles to the facts analyses may give qualitative, semiquantitative, or quanti-
of the case at hand will likely be useful in the determina- tative results.
tion of whether toxicologist’s testimony will or will not be Many contemporary analytical chemistry procedures
admissible as evidence. The factors that the court uses to performed in each of the above-mentioned laboratory
make this determination are discussed in the expert wit- types allow detection of the presence of chemicals in
ness section at the end of this chapter. biological samples that represent only “background” or
A toxicologist relies on analytical toxicology analyses “normal” exposure to that chemical. One example is
in many toxicology cases. In most instances, it is known micronutrients, such as vitamins A and E, copper, iron,
at the time the sample is submitted for analytical chemis- magnesium, selenium, and zinc. Similarly, lead, and with
try analysis, that the results of that analysis may be used some methods arsenic, may be detected at “background”
for legal purposes. Racing chemistry laboratories are one concentrations in blood, liver, or kidney by many analyti-
example in the veterinary profession where it is known cal toxicology methods available today. Consequently, the
from the outset that the results of the analytical chemistry detection of the chemical is not “diagnostic” for toxicosis
testing performed will be used in a legal or regulatory from that chemical, but merely indicates exposure.
enforcement setting. In some instances however, the Information beyond the concentration of a chemical in
purpose to which the results will be applied is not known, tissues is often required to reach a toxicosis diagnosis.
or perhaps that purpose changes after the testing is The distinction between “exposure to” and “toxicosis
completed. from” exposure to a chemical is fundamentally the prac-
tice of veterinary toxicology.
When the Reason for Testing the Sample Samples are received from many sources. Most diag-
Is Known nostic laboratories accept samples from veterinarians, ani-
mal owners, animal industries, state agencies, and others.
Samples are analyzed for the presence of chemical toxins The circumstances of the collection and handling of the
for many reasons and in many settings. Analyses may sample prior to submission in the diagnostic laboratory is
take place in academic, governmental, or private laborato- rarely known with certainty. Similarly, routine protocols
ries. Analyses performed in these laboratories may each in a diagnostic laboratory may be different from those in
serve a different purpose, such as research, enforcement an enforcement laboratory, particularly with respect to
actions, preclinical or other regulatory testing, clinical sample tracking, documentation, and disposal.
diagnoses, or other purposes. Some government and some private laboratories focus
Toxicology analyses in academic settings are primarily on performing chemical analyses in support of legal or
conducted to support one’s research or scholarly efforts. regulatory enforcement actions. Examples of such labora-
One example is the development of new analytical meth- tories include racing chemistry laboratories, and State or
ods. Another example is the characterization of adverse Federal Departments of Agriculture or Health. Many of
effects of a particular dose of a particular chemical in a these laboratories have inspectors who insure proper sam-
given species. Similarly, researchers may observe the ple collection and transport to the laboratory. In addition,
clinical signs and adverse effects of animals exposed to sample tracking, control, retention, and disposal are
chemicals, then compile these effects in retrospective or generally better documented in laboratories devoted to
prospective case reports in the peer-reviewed literature. enforcement action, than those devoted to research or
Such literature may be useful to support a general causa- routine diagnostic testing. The analytical methods used in
6
tion argument in a legal case. However, the medical case an enforcement setting have often have been validated
7
itself, or even the analyses performed on that medical by AOACI, or a similar entity. This validation often
6. Causation. The fact of being the cause of something produced or of
happening. The act by which an effect is produced. 7. Association of Official Analytical Chemists International