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Abstract INTRODUCTION:
This study evaluates the performance of two immunoassay-based point of care testing (POCT) kits for urine drug screening in remote clinics where access to advanced technologies like liquid chromatography tandem mass spectrometry (TMS) is limited. The goal is to determine if the POCT kits can serve as a reliable first line testing approach for monitoring patient adherence to pain management programs compared to TMS.
METHODS:
Forty-six (46) medical urine samples were tested by TMS (SCIEX 6500+ QTRAP, Concord, ON, Canada), and two POCT kits, the Rapid Response™ Multi-Drug Test Panel (RR) (BTNX Inc., Markham, ON, Canada) and the SpecCheck Multi-Panel Test Cup (SC) (Spectrum Medical Diagnostics, Mississauga, ON, Canada). Both POCT kits use lateral flow immunoassay, where labeled drug-protein conjugates compete with drugs in urine for antibody binding sites on a membrane strip. Drugs detected and their respective cutoff concentrations (in ng/mL) were (TMS, RR, SC): cocaine metabolite (benzoylecgonine) (100, 150, 150), methamphetamine (250, 1000, 500), amphetamine (250, 1000, 500), benzodiazepines (100, 300, 300), methadone metabolite (EDDP: 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine) (100, 100, 100), buprenorphine (40, 10, 10), morphine (300, 300, 300), hydromorphone (100, 500, 250), oxycodone (100, 100, 100) and fentanyl (10, 10, 20).
RESULTS:
TMS detected the following true positives across the 46 samples: benzoylecgonine (17), methamphetamine (7), amphetamine (19), benzodiazepines (18), EDDP (9), buprenorphine (10), morphine (9), hydromorphone (23), oxycodone (7), and fentanyl (2). Several discrepancies were noted when comparing POCT with TMS. Below, the term POCT refers to scenarios where both RR and SC yield the same result, either negative or positive.
All 17 TMS-positive samples for benzoylecgonine were detected by POCT. However, one additional sample, which was below the TMS cutoff, tested positive with POCT despite the higher POCT cutoff, indicating a false positive.
All 7 TMS-positive samples for methamphetamine were detected with RR, but two with low concentrations (<250 ng/mL and 293 ng/mL) tested negative with SC, indicating stricter SC cutoff adherence. Amphetamine, detected in 19 samples by TMS (either alone or as a metabolite of methamphetamine), was consistently identified by both POCT kits. Notably, five of these samples were below the RR cutoff, and two of these, were also below the SC cutoff. One sample without amphetamine, but with high hydroxy bupropion (metabolite of bupropion and a known interferent), tested negative by POCT, indicating low cross reactivity in this case.
POCT showed good agreement for benzodiazepines with TMS for six samples containing diazepam metabolites (nordiazepam, oxazepam, and temazepam), and one with only oxazepam. Five of six lorazepam-only samples were POCT positive, four above the POCT cutoff, and one (120 ng/mL) below. A sample with 145 ng/mL lorazepam tested positive only with RR, indicating variability near the cutoff. Four out of five samples with only 7-amino clonazepam (metabolite of clonazepam), tested negative with POCT; three were below the POCT cutoff (233, 298 and 111 ng/mL) while one was above (620 ng/mL). Another sample with 947 ng/mL tested negative with SC, suggesting a ~20% false negative rate for clonazepam detection for POCT.
Eight out of nine EDDP-positive samples by TMS were detected by both POCT assays. One at 256 ng/mL, tested negative with POCT (false negative), and one TMS-negative sample tested positive with RR (false positive).
All ten buprenorphine-positive samples with TMS were detected by POCT. Additionally, one sample negative for buprenorphine but positive for norbuprenorphine (125 ng/mL), tested positive with POCT. Another sample negative for both buprenorphine and norbuprenorphine, tested positive with RR, indicating a likely false positive.
All nine TMS-positive samples for morphine were also detected by POCT, eight of these also contained hydromorphone. Ten additional samples that were morphine-negative but had high hydromorphone levels, tested positive for morphine with POCT, indicating false positives for morphine, due to poor differentiation between morphine and hydromorphone in POCT. One sample with neither morphine nor hydromorphone, tested positive for morphine by POCT. Hydromorphone was detected in 24 samples by TMS. Of these, 16 contained hydromorphone as the primary drug with no morphine, while 8 contained hydromorphone as a metabolite of morphine. One sample with high morphine, but no hydromorphone, tested positive for hydromorphone with POCT, while another sample with high hydromorphone tested negative with POCT. Four samples with no morphine or hydromorphone tested negative with RR, but positive with SC; two of these contained oxymorphone, however, four other oxymorphone-containing samples tested negative for hydromorphone across all methods. Oxycodone was detected in 7 samples, without morphine or hydromorphone. However, 3 other samples without oxycodone, but with high hydromorphone, tested positive for oxycodone with POCT. One more sample tested positive only with SC, indicating possible false positives due to hydromorphone interference. The two fentanyl positive samples detected by TMS showed consistent results across the assays.
CONCLUSION:
Two POCT kits, Rapid Response (RR) and SpecCheck (SC), were evaluated against TMS for urine drug screening. While POCT provides rapid, cost-effective results, it is prone to both false positives (e.g., morphine when high hydromorphone is present) and false negatives (e.g., missed clonazepam detection due to lack of sensitivity to 7-amino clonazepam), requiring cautious interpretation. Both kits demonstrated limitations in reliably distinguishing between certain opiates (especially SC) and detecting specific benzodiazepines, suggesting TMS may be needed for confirmation when POCT results are inconclusive.
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= Discovery stage. (53.14%, 2025)
= Translation stage. (22.33%, 2025)
= Clinically available. (24.53%, 2025)
