Table 2.

Comparing risk behavior variables among Seattle-area IDU participating in the NHBS-IDU1 and NHBS-IDU2 surveys

	NHBS-IDU1 RDS adjusted estimate		NHBS-IDU2 RDS adjusted estimate		p-value (with RDS weighting)1
Year	2005		2009
	%	95% C.I.	%	95% C.I.
Drug-associated behavior2
Drug most frequently injected
Heroin	68	(64 – 82)	81	(71 – 88)	1 × 10−5
Speedballs	8	(5 – 13)	8	(4 – 12)
Cocaine	8	(3 – 14)	4	(1 – 9)
Amphetamines	17	(4 – 19)	7	(2 – 16)
Shared syringe	34	(26 – 42)	25	(19 – 33)	.05
Shared cooker	62	(52 – 72)	53	(46 – 61)	.01
Backloaded	28	(20 – 37)	34	(28 – 42)	.50
Sexual behavior
Male-to-male sex2	6	(3 – 8)	15	(7 – 24)	3 × 10−5
Number sex partners2
0	17	(12 – 24)	21	(15 – 28)	.32
1	38	(28 – 47)	33	(26 – 40)
2 – 4	30	(21 – 41)	32	(25 – 40)
5 – 9	7	(4 – 10)	7	(3 – 10)
10 +	8	(4 – 13)	7	(4 – 14)
Unprotected, non-concordant anal or vaginal sex at last sexual contact3	19	(9 – 26)	32	(24 – 44)	5 × 10−4
HIV and HCV-related variables
HIV testing4
In previous 12 months	65	(55 – 74)	48	(39 – 56)	2 × 10−6
In previous 3 months	29	(20 – 38)	14	(8 – 18)	4 × 10−7
Self-reported HIV status
Negative	94	(91 – 97)	79	(72 – 85)	9 × 10−14
Positive	0.4	(0.1 – 1)	7	(3 – 12)
Unknown	6	(3 – 8)	15	(10 – 21)
Self-reported HCV status
Negative	28	(19 – 38)	30	(23 – 38)	0.20
Positive	59	(48 – 69)	58	(50 – 66)
Unknown	14	(7 – 22)	12	(8 – 16)
N (total)	368		497

¹Based univariate logistic regression incorporating RDSAT generated individual weights.

²In the previous 12 months

³Among participants reporting sexual contact in the previous 12 months.

⁴Among participants not self-reporting HIV-positive status.