Laboratory Question for the Week of April 17, 2023

Question:

Can you explain more of the rationale behind the term “drug of abuse?”

Answer:

The terms “drug abuse” or “substance abuse” is defined as the use of chemical substances that lead to an increased risk of problems and an inability to control the use of the substance. Drugs prescribed with the intention to be therapeutic can be abused either by the patient for which they were prescribed for – or by another person who has access to the prescription. Some of the monitored drugs tend to have a narrow “therapeutic index,” which is a ratio between the toxic and therapeutic (effective) dose of medication. Drugs or classes of drugs may be assayed by presumptive (qualitative) testing. A presumptive test may be followed by definitive (quantitative) testing when there is an unexpected or inconsistent finding from the presumptive test. This is medically necessary to determine the presence or absence of drugs or drug classes. They can be generally reported as negative or positive. Presumptive methodologies include simple-to-use point-of-care (POC) devices as well as more sophisticated analysis for competitive immunoassays (IA) and thin-layer chromatography. There should be a direct correlation between those positive findings generated from presumptive testing and those requested definitive tests to specifically confirm such findings. Definitive methods will quantitatively report the results of drugs as absent or as present in concentrations of nanograms per milliliter (ng/ml). Definitive methods for urine drug of abuse testing are limited to GC-MS and LC-MS/MS testing methods only.