chewing. Stimulation by placing a lemon drop in the mouth (acidic stimulation) may increase flows to 5 to 10 mL/min. Some collection device pads are also impregnated with buffers that stimulate OF production. Stimulation should be avoided because it increases production and may dilute drugs and metabolites in the OF. Te effects of OF stimulation are similar to those of over- hydration on detecting drugs in urine. OF specimens may be sufficiently dilute that drug concentrations are less than that of the cutoff and, therefore, not reportable. Although some OF collection methods


have the donor “spit” into a collection tube, most are performed with specially designed collection devices. Tese devices are rea- sonably similar in design across manufac- turers and have an absorbent pad atached to a handle. Te pad is placed in the donor’s mouth, OF is collected and the pad con- taining the OF is placed in a transport ves- sel that usually contains a drug-stabilizing liquid. Te vessel and contents are sent to the laboratory for testing. When OF is collected by spiting, the


volume collected is apparent. When OF is collected using an absorbent device, the volume obtained is much less obvi- ous. Previous studies have shown that OF collection volumes were device dependent. Some devices collected less than 1 mL, while others approached a 2 mL collection volume. With large specimen volumes such as those obtained from urine collections, laboratories can perform several analyses and retests if needed. However, with the limited volume of OF, a conservative ap- proach to laboratory testing is needed to ensure adequate specimen for all testing. Importantly, studies have also shown


that when different manufacturer’s devices were evaluated using repetitive collections, the volume collected sometimes varied more than 25 percent. Te reporting cutoff is applied and quantitative concentrations are reported per mL of OF.


Cutoff concentrations and laboratory


results for drugs in OF are expressed in ng/ mL (i.e. ng of drug/milliliter of OF). If the volume of OF collected is unknown or vari- able, the cutoffs and the laboratory results become ambiguous. Te reproducibility of volume of OF collected is critical. Labora- tories strive to report quantitative results with scientifically acceptable precision (+20 percent). Meaning that if the mea- sured concentration of a drug in OF was 10 ng/mL, and the laboratory analyzed the sample multiple times, its goal would be to obtain results between 8 and 12 ng/mL. However, if the volume of OF collected is too variable the laboratory’s analytical precision is compromised.


Many devices absorb OF, but it must be harvested from the device for analysis. Therefore, once collected, how much of the OF can be recovered from these devices?


Some absorbent devices are placed in the


donor’s mouth for a period of time predeter- mined by the device’s manufacturer. Once the device is removed from the mouth it is compressed by hand or laboratory centrifu- gation and the OF “harvested”. Studies have shown that the volume of OF is harvested from these devices varied from less than 20 percent (of that collected) to approximately 80 percent. Clearly, this variability exceeds that desirable to ensure a sufficient volume for testing when most devices collect be- tween 0.8 and 2 mL of OF. Alternate commercial collection device


kits contain a drug-stabilizing liquid or buffer. Once the required volume of OF is collected, the device is removed from the donor’s mouth and placed in a transport tube containing the buffer. An advantage of these devices is that the unpleasantness and variability of post collection “harvest- ing” is avoided. Tese devices also may have a volume indicator that changes color when a predetermined volume OF volume


www.datia.org datia focus 11


has been collected. Te volume indicator provides beter assurance that a consistent volume has been collected. However, once the collection device is placed in a trans- port tube, the volume of OF in the device is diluted by the buffer. For example, the device collects 1 mL of OF and the trans- port tube contains 2 mL of buffer; drugs in the donor’s OF are then diluted 1 part in a total volume of 3 parts. Enter an additional collection variable—the volume of buffer in the transport tube. Tis volume should be precisely controlled by the manufac- turer, but could vary if the manufacturer’s processes are not adequately controlled. Te buffer volume may also vary if there is leakage during the collection or handling. Terefore, care should be taken to ensure that the buffer volume is preserved during the OF collection.


Once absorbed onto the device, can drugs in the OF be recovered?


Drugs may be absorbed or otherwise


adhere to certain materials or surfaces during OF collection and handling—such as the collection pad on the device. Once “absorbed”, these drugs are essentially removed from the OF and can not be detected by routine laboratory procedures. For example, at collection a drug was pres- ent in the donor’s OF at a concentration of 100 ng/mL. However, because the collec- tion device “absorbed” retained one-half of the drug, the measured concentration in OF was 50 ng/mL.


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