Table 1.

Description of cohort by DTR test.

	Opiate positive (N = 18,965)	Test negative (N = 78,838)	p-value*
Index test result (%)
Negative opiates and cocaine	(0)	78,838 (100)
Opiate positive, cocaine negative	7259 (38)	(0)
Opiate positive, cocaine positive	11,706 (62)	(0)
Gender (%)			0.23
Female	4614 (24)	18,854 (24)
Male	14,351 (76)	59,984 (76)
Median age at test [IQR]	29.9 [25.8–34.4]	24.0 [20.2–30.0]	<0.001
Median number of past crimes [IQR]	25 [8–50]	3 [0–13]	<0.001
Median age at first recorded offence [IQR]	16.9 [14.7–19.5]	17.1 [14.7–20.3]	<0.001
Type of crime at first recorded offence (%)*
Violence offences	1300 (10)	6713 (14)	<0.001
Serious acquisitive	2595 (21)	7693 (16)	<0.001
Non-serious acquisitive	5059 (40)	17,390 (37)	<0.001
Other	3593 (29)	15,226 (32)	<0.001
Missing age of initiation (%)	6238 (33)
No linked NDTMS record	4530 (24)
Missing age of initiation within NDTMS record	1708 (9)
Median age of initiation [IQR]	19 [17,23]
Males	19 [17,23]
Females	19 [16,22]

^**Categories not mutually exclusive.

^*p-value from chi-squared test, for test of proportions, or the Mann-Whitney test, for test of medians.