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Medical toxicology addresses harm caused by acute and chronic exposures to excessive amounts of a xenobiotic. The management of toxicologic emergencies is a major component of medical toxicology. Detecting the presence or measuring the concentration of xenobiotics and other acutely toxic xenobiotics is the primary activity of the analytical toxicology laboratory. Such testing is closely intertwined with therapeutic drug monitoring, in which drug concentrations are measured as an aid to optimizing drug dosing regimens. In addition to drugs, measurements may be made of a variety of xenobiotics such as pesticides, herbicides, and poisons found in plants, animals, or the environment. The toxicology laboratory is frequently viewed in much the same way as other clinical laboratories often are—as a "black box" that converts orders into test results. Because toxicology testing volumes are relatively low and menus are extensive, testing is not as highly automated as in other clinical laboratories. Many results may be "hand-made the old-fashioned way." The downside of this may be somewhat longer turnaround times. But the upside is that toxicology laboratory personnel have the incentive and flexibility to develop substantial expertise. Medical toxicologists who understand how toxicology testing is done will be able to apply the results more effectively.

Despite a common focus, there is remarkable variability in the range of tests offered by analytical toxicology laboratories. Test menus may range from once-daily testing for routinely monitored drugs and common drugs of abuse to around-the-clock availability of a broad array of assays with the theoretical potential to identify several thousand compounds. Recently, consensus documents have been developed that recommend tests that should be available to support management of poisoned patients presenting to emergency departments.22,37 Although they make specific recommendations, these guidelines recognize that no set of recommendations will be universally appropriate and note that it is impossible for a clinical laboratory to offer a full spectrum of toxicology testing in real time.

Decisions on the menu of tests to be offered by any specific laboratory should be decided by the laboratory director in consultation with the medical toxicologists and other clinicians who will use the service and should take into account regional patterns of use of licit and illicit drugs and environmental toxins, as well as resources available and competing priorities.

The recommendations in Table 6–1 were developed by the National Academy of Clinical Biochemists (NACB) from a consensus process that involved clinical biochemists, medical toxicologists, forensic toxicologists, and emergency physicians.37 Although these tests should be readily available in the clinical laboratory, they should not be considered as a test panel for possibly poisoned patients. As with all laboratory tests, they should be selectively ordered based on the patient's clinical presentation or other relevant factors. Suggested turnaround time for reporting serum concentrations of the drugs listed in Table 6-1 was 1 hour or less. Quantitative tests for serum methanol and ethylene glycol were also recommended, with the reservations that these tests are not ...

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