Analytic Testing
Analytic testing can be used to provide a definitive answer, but it must be used correctly and the results analyzed judiciously. Samples should not be sent to an analytic laboratory without some knowledge and forethought.
The analytic laboratory will need guidance in terms of what they are testing for, as well as a history including the time since intoxication, dose of toxicant, and postmortem changes. Urine is the gold standard, especially for drug identification, but serum and plasma can also be used for analysis. Different forms of instrumentation and analyses are used for specific substances. For example, metals such as lead, zinc, arsenic, and others are analyzed with atomic absorption and spectrometry.6 Enzyme-linked immunosorbent assay screens are generally sensitive, but the risk of cross-reaction with other substances may be large.6 Drugs, many pesticides, and plant toxins are analyzed using gas or liquid chromatographymass spectrometry, but unless specifically requested, the results are generally not quantitated and only demonstrate the presence of a toxicant.3,5,6In summary, poisoning cases can vary from simple and direct to highly complex. It is important to investigate each one using a systematic approach, including history, clinical signs, clini- copathologic findings, and the results of analytic testing. As the veterinarian works through the investigation, each step may narrow the list of toxicants until a final answer is found. Alternatively, some investigations do not come to a conclusion, and the veterinarian is left to wonder what actually occurred. In many of these cases, environmental and management changes eliminated the toxicant before the investigation, leaving only the after effects.