Besides many other issues for collecting the samples the 3 main issues are as follows:
- Collection of an adequate volume of sample for known multiple drugs.
- Valid quantitative results as a result of good percentage recovery of drugs from the collection pad;
- Imperfect knowledge about the stability of drugs during transportation and storage.
The problem of viscosity, stability, and frothing of the saliva occurs when sample is collected by expectoration; therefore a collection device is preferred to collect an ample homogeneous sample for drug testing. There are a number of collection device successfully in use in the United States. Some of which consist of a simple cotton pad, whereby the neat oral fluid is removed using centrifugation methods or organic solvent in the laboratory (e.g., Finger collector; Salivette®). In these cases, the volume of oral fluid collected is not adequate for multiple drug analysis so it requires using 2 separate techniques in workplace drug testing. Secondly, use of an organic solvent to remove the drugs from the pad, although efficient, adds another stage to the process, particularly if immunoassay is the initial test, since organic solvents are not conducive to immunochemical screening.
Some other, more complicated devices consist of a pad, which absorbs the saliva, and then the whole collector is placed into a stabilization buffer for transportation to a laboratory for processing (e.g., Quantisal™, Omni-Sal®, Intercept®). A typical saliva sample collection device is shown in Figure 7-2. Some devices incorporate a dye into the stem of the collector, which turns blue when 1 mL (±10%) of neat oral fluid has been collected.
Figure 7-2: Typical oral fluid collection device, showing collection pad and stabilization buffer.
This provides an adjustment for the dilution factor is made on the basis for a valid quantitative analytical result. Oral fluid is being used increasingly as a specimen of choice for drug detection and its various applications due to the known amount of sample volume and high percentage of drug recovery from the collection pad.
In 2005, Crouch reported that collection was one of the major variable in oral fluid testing. The paper presented the recovery of drugs from Finger Collector, Intercepts, Salivette, Hooded collector, and OralScreen® devices, with data ranging for recovery of drug as follows, 16% to 57% amphetamine, 15% to 59% methamphetamine, 61% to 97% cocaine and 33% to 50% morphine, whereas it must be noted that none of the devices were capable for the detection of THC (tetrahydrocannabinol) this is because THC tends to adhere with no trouble to cotton, plastic, and polyethylene surfaces, that be present in the laboratory equipment of collection devices, modern developments have made it possible for the manufacturer to give significant improvement in their products
In 2006, Quintela et al. reported that recoveries of opiates, amphetamine and cocaine from the Quantisal collection device were in excess of 90%, whereas the THC recovery also acceptable between 81.3% and 91.4%. A study on Salivette collector showed that much of the cocaine, morphine and 6-acetylmorphine (6-AM) was deposited on the cotton roll. Kauert et al. reported that recovery of drug including THC from the intercept device was accurate and reliable when gravimetric determination of the amount of oral fluid collected was determined. More recent journal articles require data on how efficiently the collection device is collecting the specific drug from the pads, because this information is critical for valid quantitative results for workplace drug testing.
Laboratory based oral fluid analysis requires an additional transporting phase for the samples or collected specimen to a testing facility. In consideration of the forensic cases the stability of the analytes and long term storage is an important factor. However its significant has never found to be addressed in publish ped papers. For the accuracy and efficient oral fluid testing at work place requires the following necessary improvements in the overall program as follows:
The prospective to collect grater volume of the samples, as more than one drug positives may occur, the test itself may expend, or a secondary laboratory testing may be required.
The ability to collect split samples, which is a standard practice in urine workplace testing.
In order to obtain quantitative results the known amount of oral fluid to be analyzed will also be a primary requirement.
The obligation for assessment of drug recovery from the collection pad;
The obligation for assessment of drug stability in the transportation buffer, collection vial, and long-term storage.