2.2 |. Seized drug case sample analysis

A total of 44 seized drug samples from the Anne Arundel County Forensic Services (Millersville, MD) were evaluated using both fentanyl LFIs (dipsticks, cassettes). Of these samples, 32 were determined to contain fentanyl and 12 were determined to be fentanyl-negative by gas chromatography–mass spectrometry (GC-MS) analysis. For the corresponding street samples, the LOD is less than 0.03 mg/mL for the GC/MS that was used to confirm the presence of illicit drugs. All case samples were examined with both LFI types by forensic chemists (licensed by the Maryland Department of Health) trained in using the LFIs and remained in the test laboratory’s chain of custody. Specific cutting agents within the substances were not fully reported for this study. Briefly, drug chemists diluted 10 mg of individual case samples in 1 mL HPLC-grade water (Fisher Scientific; Cat #: W5–1; Hampton, NH) and vortexed for 30 s prior to evaluation. LFI tests were then performed (dipsticks, cassettes) as stated in the Fentanyl-Specific LFIs section above and as previously described [15]. For the fentanyl dipsticks, 100 μL aliquots of each diluted sample were pipetted into the wells of a 96-well plate in triplicate. The LFIs were then dipped into the solution containing the diluted sample for 10–20 s as described in the manufacturer’s protocol. Following this, the dipsticks were placed flat on a clean, non-porous surface [15]. For the fentanyl LFI cassettes, the tests were first placed flat and 120 μL of diluted sample (per the manufacturer’s recommendation) was pipetted into the sample well of the test cassette [15]. All procedures were performed under the appropriate engineering controls (i.e., chemical fume hood) with the operators wearing the recommended personal protective equipment (i.e., gloves, eye protection). Both the dipsticks and cassettes were scored positive or negative 5–10 min following exposure to the diluted case samples as stated in the manufacturer’s protocol. For data analysis, a single positive (of the three sample replicates) was considered a positive detection for that sample; this was the scoring approach due to variation in detection of fentanyl in samples at or near the LOD. As the sample reaches closer to the LFI’s LOD, the tests will produce both positive and negative results. Any positive results would indicate the presence of fentanyl in the tested sample above the assays LOD. In addition, calculations were performed to determine sensitivity (ability to determine the presence of fentanyl), specificity (ability to determine the absence of fentanyl), and efficiency (ability to determine the presence or absence of fentanyl) of the fentanyl LFIs for each condition (either seized drugs or postmortem urine) [18]. These calculations were based on the presence of true positives (TP, correct indication of fentanyl), false positives (FP, incorrect indication of fentanyl), true negatives (TN, correct indication that no fentanyl is present), and false negatives (FN, results indicate that no fentanyl is present above the GC-MS detection cutoff). The formulas for these outputs are shown below:

Finally, results were noted and documented with a digital camera.