Toxicology addresses harm caused by acute and chronic exposures to excessive amounts of a xenobiotic. Detecting the presence or measuring the concentration of 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. 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 “handmade the old-fashioned way.” A 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. Clinicians who understand how toxicology testing is done will be able to order more judiciously and apply the results more effectively.
RECOMMENDATIONS FOR ROUTINELY AVAILABLE TOXICOLOGY TESTS
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. Consensus statements have recommended tests that should be available to support management of poisoned patients presenting to emergency departments.21,32 These guidelines make specific recommendations but recognize that no set of recommendations will be universally appropriate and 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 exposure to 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.32 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 history, clinical presentation, or other relevant factors. Suggested turnaround time for reporting serum concentrations of the drugs listed in Table 6–1 was one hour or less. Quantitative tests for serum methanol and ethylene glycol were also recommended, with the reservations that these tests are not needed in all settings and that a realistic turnaround time is 2 to 4 hours. Serum cholinesterase testing with a turnaround time of less than 4 hours ...