Drug testing, especially testing when
Drug testing, especially testing when there are potential legal implications, is a multifaceted process.
there are potential legal implications, is a multifaceted process. Key to testing, obtaining reliable results and defending the results is the collection of a representative specimen. Previous experiences with blood collections have demonstrated that drug concentrations vary by collection site, type of collection container, and stability of the drug and specimen handling conditions. It is well chronicled that drugs may re-dis- tribute in the body aſter death such that the post-mortem blood-drug concentrations may not accurately reflect those at the time of death. It is also well documented that many drugs and drug metabolites are not stable and must be collected, stored and handled using inert containers and special preservatives (e.g. ethanol and cocaine). Urine drug concentrations vary by hydra-
tion state of the donor, quality of the collec- tion vessel, stability of the drug and storage and shipping conditions of the specimen. Overhydrated donors produce dilute specimens that may contain artificially low concentrations of drug. Specimens may be sufficiently dilute that drugs are not detected or their concentration is less than that of the cutoff and, therefore, not report- able. Dehydrated donors have artificially elevated drug and metabolite concentra- tions, which may increase detecting their drug use. Tis article does not endorse a specific collection technique or device.
The specimen In the scientific literature and our daily
discussions, the terms saliva, oral fluid and oral fluids are used inconsistently and interchangeably. Saliva is the fluid secreted by individual glands distributed through- out the oral cavity. Once saliva from the individual glands is pooled and mixed with other materials in the mouth the terms “oral fluid” or “oral fluids” are more appropriate. Once produced, OF can be “spit” into a collection vessel, suctioned or swabbed
10 datia focus
from the mouth or absorbed onto a col- lection device. During the development of OF as a testing specimen, many collection devices have been marketed to which the following considerations apply. 1. What volume of OF does the device collect?
2. How reproducible is the volume collected?
3. Many devices absorb OF, but it must be “harvested” from the device for analysis. Terefore, once collected, how much OF can be recovered from these devices?
4. Can drugs absorbed onto the device be recovered and detected?
5. How stable are drugs in OF once collected?
Answering these questions is essential
for clients, collectors and laboratories considering OF testing. For example, minimum urine volume collections are in 10s to 100s of mLs, but OF devices rarely collect more than 1 to 2 mLs. Among other concerns, the smaller OF volume may limit the number of tests that can be performed by the laboratory. For those devices that work by absorbing the specimen, requiring harvest of the specimen from the machine, the volume of OF recovered has similar implications. Variability of the volume of OF collected will result in variability of measured drug concentrations. If the drug is not stable in collected OF, detection will be compromised. Inability to recover drugs from the collection device will affect drug detection and quantification.
What volume of fluid does the device collect? How reproducible is the volume collected?
Some collection techniques purposeful-
ly, or inadvertently, “stimulate” OF produc- tion to increase the volume collected. OF production may be stimulated by “mechan- ical” means such as chewing gum. Typical OF flows are 0.05 mL/min while sleeping, but increase to 1 to 3 mL/min while
spring 2013
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