By Susanne Meyer Parks, CQE
Profile-II ER is a single-step immunochromatographic test for the qualitative detection of cannabinoids (THC), cocaine, opiates, amphetamines, phencyclidine (PCP) barbiturates, benzodiazapines, tricyclic antidepressants, and methadone in human urine. It detects THC, cocaine, amphetamines and PCP based on the Substance Abuse and Mental Health Administration’s (SAMHSA) recommended cut-off levels, and it detects opiates below the SAMHSA recommendations. There are no SAMHSA-recommended cut-off concentrations for barbiturates, benzodiazapines, tricyclic antidepressants, methadone and/or their metabolites. (See table for test cut-off concentrations.) As with all on-site drugs-of-abuse tests, Profile-II ER provides only a preliminary analytical test result. A more specific method, such as gas chromatography/mass spectrometry (GC/MS) or high performance liquid chromatography (HPLC) must be used to obtain a confirmed analytical result.
Profile-II ER utilizes colloidal gold as the detection system. Gold colloids have been used in immunoassays for more than 20 years. Gold colloids are a suspension of finely divided particles of gold in a buffered solution. The small particles have optical properties that display various colors. The gold colloids in this test emit a natural red color that lends itself to single-step on-site assays. This simple-to-use technology has been used successfully in over-the-counter tests such as home pregnancy tests. Results are easy to interpret and obtained quickly. Two drops of urine are added to each sample well and results are read after seven minutes.
The test combines gold colloid technology with monoclonal antibodies in a competitive inhibition format to detect the presence of a drug in urine. Mouse monoclonal antibodies that are specific for each of the nine drugs bind to gold colloid particles. This mixture is dried on one of two test strips near the sample wells in the device. Two drops of urine are applied to both sample wells on the test strips which mobilizes the gold colloid. If the urine sample contains one or more drugs, the monoclonal antibodies will bind to them. Further down the strip, each of the drugs is immobilized at the location which corresponds to the labels on the device. The gold/monoclonal antibody/urine complex then migrates down the strip via capillary action. If the urine contains one or more of the drugs, these drugs will bind to the limited number of binding sites on the antibody/gold complex, thus the monoclonal antibody will not be available to bind to the drug on the test strip. Thus, the absence of color indicates a preliminary positive result. On the other hand, if the urine sample is drug-free, the monoclonal antibodies are free to bind to the immobilized drug. Since the monoclonal antibodies are coupled to the gold particles, a colored line will appear on the strip indicating a negative result.
In addition to lines for the drugs, there is an internal control line for each of the two strips. An anti-mouse antibody is immobilized on the strip. When the monoclonal antibody-coated gold particles pass over this region, a line develops indicating sample has flowed across the strip correctly and that conditions are suitable for immunological reactions.
The performance of Profile-II ER was analyzed in comparison to alternate testing methodologies for accuracy. Data showed equivalence to a laboratory-based test and GC/MS. With respect to tricyclic antidepressants, HPLC is the primary method of detection. All comparison testing of tricyclic antidepressants is to the HPLC method. The overall accuracy when compared to a laboratory test ranged from 98 to 100 percent. When percent agreement between positive samples was analyzed, data ranged from 95 to 100 percent. When percent agreement between negative samples was analyzed, data ranged from 99 to 100 percent. The table lists specific results.
When the accuracy of Profile-II ER was compared to GC/MS, the results ranged from 98 to 100 percent. Again, the table lists specific results. As mentioned above, tricyclic antidepressants were analyzed with HPLC for this study.
The precision of Profile-II ER was assessed around the specific cut-off for each drug by evaluating standard drug solutions spiked into drug-free urine. At 25 percent above the cutoff, the precision for THC was 95 percent, cocaine 100 percent, opiates 100 percent, amphetamines 100 percent and PCP 98 percent. At 50 percent above the cutoff, the precision for tricyclic antidepressants was 98 percent, barbiturates 100 percent, methadone 96 percent and benzodiazapines 100 percent.
In a separate independent study at MedTox Laboratories, the performance of Profile-II ER was compared to the current market leader. One hundred samples were tested on both devices. The overall agreement was 97 percent.
The test comes in boxes of 25 devices, each of which is individually foil wrapped with a pipette.
Profile-II ER is manufactured by MedTox Scientific, which originated from a 1996 merger between MedTox Laboratories and EDITek.
It is produced at the former Burlington, N.C. EDITek manufacturing plant, now known as MedTox Diagnostics. MedTox Diagnostics has been developing on-site drug testing products since 1987 when it became the first company to receive FDA clearance for an on-site drugs-of-abuse kit, EZ-Screen Cannabinoid. MedTox Laboratories was among the first ten laboratories to be granted federal certification by the U.S. Department of Health and Human Services for federally mandated drug testing. It is certified by the Substance Abuse and Mental Health Administration.
Susanne Meyer Parks is a Certified Quality Engineer and Manager of Quality Systems at MedTox Laboratories in Burlington, N.C.
For more information about the Profile-II ER, Select Reader Service Number 260, go to their Web site (www.medfox.com ) or call 651-636-7466.