Accuracy of substance exposure history in patients attending emergency departments after substance misuse; a comparison with biological sample analysis

Figures & data

Table 1. Number and percentage of included participants reporting use of specific compounds^a at the time of admission and numbers in which these substances were detected by HRAM LCMS in at least one sample.

Substance	n (%) reported	n (%) detected
SCRA	171 (36.0%)	151 (31.8%)
Heroin	67 (14.1%)	108 (22.7%)^b
Cocaine	56 (11.8%)	70 (14.7%)
MDMA	53 (11.1%)	67 (14.1%)
Amphetamine	10 (2.1%)	37 (7.8%)
LSD	8 (1.6%)	6 (1.3%)
Alprazolam	7 (1.4%)	28 (5.9%)
Ketamine	6 (1.2%)	42 (8.9%)
Mephedrone	4 (0.8%)	5 (1.1%)^c
Fentanyl	0 (0.0%)	35 (7.4%)

^aNote that assays used did not reliably detect evidence of tetrahydrocannabinol (THC) or Gamma hydroxybutyrate (GHB and related compounds prior to 2020, so these substances are not considered in our analysis.

^bThe presence of the selected heroin/morphine metabolites monoacetyl morphine, morphine, or morphine conjugates was considered evidence of heroin exposure.

^cAnalytical methods used do not distinguish 3- from 4-methylmethcathinone, although in a UK context 4-methylmethcathinone (mephedrone) is the prevalent compound.

Table 2. Numbers of patients reporting single substance use by age group, sex and reported routes of exposure for the four most common reported drug types.

	SCRA			Heroin			Cocaine			MDMA
	Male	Female	Total	Male	Female	Total	Male	Female	Total	Male	Female	Total
Routes
Oral	8	1	9	1	1	2	5	2	7	30	19	49
Smoked	107	21	128	14	2	16	5	1	6	0	0	0
Insufflated	8	0	8	3	0	3	28	7	35	1	0	1
Intravenous	1	0	1	28	7	35	1	0	1	1	0	1
Other/unknown	24	3	27	11	3	14	7	1	8	1	1	2
Age distribution
16–25	23	7	30	5	0	5	12	2	14	26	17	43
26–35	53	6	59	9	4	13	16	4	20	6	2	8
36–45	44	9	53	19	7	26	5	2	7	1	1	2
46–55	12	4	16	16	1	17	10	1	11	0	0	0
56–65	9	0	9	3	1	4	2	0	2	0	0	0
>65	1	0	1	2	0	2	1	1	2	0	0	0
Age unknown	3	0	3	0	0	0	0	0	0	0	0	0
Total	142	26	171	54	13	67	46	10	56	33	20	53

Figure 1. Numbers of separate substances identified by analysis in all those reporting single drug exposure (Panel A) and those reporting SCRA (Panel B), heroin (Panel C), cocaine (Panel D) and MDMA (Panel E).

Table 3. Most commonly detected substances in biological samples of patients reporting use of a single drug when this was a SCRA, cocaine, heroin or MDMA.

Drugs reported	SCRA (n = 171)	Cocaine (n = 56)	Heroin (n = 65)	MDMA (n = 53)
Drugs detected (including metabolites*)
SCRA	121 (70.8%)	1 (1.8%)	12 (18.5%)	3 (5.7%)
Cocaine	9 (5.3%)	46 (82.1%)	16 (24.6%)	3 (5.7%)
MDMA	7 (4.1%)	1 (1.8%)	1 (1.5%)	44 (83.0%)
Fentanyl	15 (8.8%)	3 (5.4%)	5 (7.7%)	5 (9.4%)
Heroin	19 (11.1%)	6 (10.7%)	32 (49.2%)	1 (1.8%)
Codeine	13 (7.6%)	14 (25%)	29 (44.6%)	2 (3.8%)

*See methods for details of metabolites.

Agreement between reported and analytically-confirmed exposure is marked in bold.

Table 4. Accuracy of reported exposure to SCRA, cocaine, heroin or MDMA in 473 patients reporting single substance exposure and attending emergency departments with toxicity.

	SCRA	Cocaine	Cocaine	Heroin	MDMA
(A) All routes of exposure	Parent drug/metabolites	Parent drug/metabolites	Parent drug only	Parent drug/metabolites	Parent drug/metabolites
Use reported	171	56	56	65	53
Use detected	151	172	70	108^a	70
Reported and detected (true positive)	121	46	22	41	44
Reported but not detected (false positive)	50	10	34	24	9
Not reported but detected (false negative)	30	126	48	67	26
Not reported and not detected (true negative)	273	292	370	342	395
Sensitivity (95% CI)	80.1% (72.9–86.2%)	26.7% (20.3–34.0%)	31.3 % (20.9–43.6%)	38% (28.8–47.8%)	62.9% (50.5–74.1%)
Specificity (95% CI)	84.5% (80.1–88.3%)	96.7% (94.0–98.4%)	91.6% (88.4–94.1%	93.4% (90.4–95.7%)	97.7% (95.8–99.0%)
Positive predictive value	70.8% (65.0–76.0%)	82.1% (70.4–89.9%)	39.3% (28.7–50.9%)	63.1% (52–72.9%)	83.0% (71.4–90.5%)
Negative predictive value	90.1% (86.8–92.6%)	69.9% (67.9–71.8%)	88.5% (86.7–90.0%)	83.6% (81.4–85.5%)	93.8% (91.8–95.4%)
Accuracy	83.1% (79.4–86.4%)	71.3% (67.0–75.3%)	82.7% (79.0–86.0%)	80.8% (77.0–84.3%)	92.6% (89.9–94.8%)
	SCRA smoked	Cocaine snorted	cocaine snorted	Heroin IV	MDMA Oral
(B) Use by specific route	Parent drug/metabolites	Parent drug/metabolites	Parent drug only	Parent drug/metabolites	Parent drug/metabolites
Use reported	128	35	35	35	49
Use detected	98	37	17	25^a	48
Reported and detected (true positive)	95	31	14	21	41
Reported but not detected (false positive)	33	4	21	14	8
Not reported but detected (false negative)	3	6	3	4	7
Not reported and not detected (true negative)	343	433	436	435	418
Sensitivity (95% CI)	96.9% (91.3–99.4%)	83.8% (68–93.8%)	82.4% (56.6–96.2%)	84% (63.9–95.5%)	85.4% (72.2–93.9%)
Specificity (95% CI )	91.2% (87.9–93.9%)	99% (97.7–99.8%)	95.4% (93.1–97.1%)	96.9% (94.8–98.3%)	98.1% (96.3–99.2%)
Positive predictive value	74.2% (67.5–80.0%)	88.6% (74.3–95.4%)	40% (29.4–51.7%)	60% (46.6–72.1%)	83.7% (71.9–91.1%)
Negative predictive value	99.1% (97.4–99.7%)	98.6% (97.2–99.3%)	99.3% (98.1.2–99.8%)	99.1% (97.8–99.6%)	98.4% (96.8–99.2%)
Accuracy	92.4% (89.6–94.6%)	97.9% (96.2–99%)	94.9% (92.6–96.7%)	96.2% (94.0–97.7%)	96.8% (94.8–98.2%)

(A) Considering all reported routes of exposure (B) considering one specific route of exposure.

^aThe presence of the selected heroin/morphine metabolites monoacetyl morphine, morphine, or morphine conjugates was considered evidence of heroin exposure.