Volume 6, Issue 1, July 2011
Dr W. T. Poon
Associate Consultant, Department of Pathology, Princess Margaret Hospital
Toxicology analysis involves detection, identification and measurement of foreign compounds and their metabolites in biological and other specimens. It plays a useful role in them a nagement of poisoned patients when the diagnosis is in doubt, the administration of antidotes or protective agents is contemplated, or the use of active elimination therapy is being considered. As the scope and complexity of clinical toxicology continues to increase, continuing effort is required for the laboratory to expand its diagnostic capability and coverage. Apart from patient care, identification of a lethal or emerging toxin also serves to provide useful information for toxico-vigilance of potential public health threats and helps to prevent further poisonings. Some common and important herbal poisonings that have occurred in Hong Kong would be discussed as examples.
Apart from poisoning diagnosis, laboratory test can be used to predict the risk of adverse event to drugs in individual patients. It is now feasible to identify the genetic basis for certain toxic side effects and drugs will then be prescribed only to those who are not genetically at risk. Theranostic is the term used to describe the process of diagnostic therapy for individual patients - to test them for possible reaction to taking a new medication and to tailor a treatment for them based on the test results. In Hong Kong, genotyping for human lymphocyte HLA-B*1502 is recommended prior to administering carbamazepine for patients in order to avoid the development of Stevens-Johnson syndrome. An increasing number of pharmacogenetic tests are now available for clinical application. The criteria required of a pharmacogenetic test to make it useful for local application would be discussed.