Table 1. Baseline individual and familial characteristics of respondents and crude odd ratios for ongoing drug use in univariate GEE models.

Characteristics			Crude OR of Drug Use
			(+) Urine Heroin Test	Reported Drug Use
I. Individual
1.1. Demographic	Mean	(95% CI)
Age	29.5	(28.9; 30.1)	0.98	0.98*
Income per month	5.78b	(5.16b; 6.40b)	1.06a	1.01a
	N	(%)
Male sex	354	(95.7)	0.74	1.13
Ethnicity: - Kinh people	348	(94.0)	0.73	0.58
Religion: - Buddhism	351	(94.9)	0.74	0.39*
Under High school education	231	(62.6)	1.34*	0.97
Married	120	(32.4)	0.87	0.65**
1.2. Morbidity
Taking ART	180	(48.7)	1.55**	1.27*
HBV	82	(22.4)	1.04	1.12
HCV	225	(61.5)	0.76	0.89
1.3. History of drug use	Mean	(95% CI)
Age at first drug use	20.6	(20.1; 21.2)	0.99	0.99
IDU length	6.7	(6.3; 7.1)	1.02	0.98
Frequency of drug use (times/day)	3.2	(3.1; 3.4)	1.76***	n/a
	N	(%)
History of drug detoxification	364	(98.4)	0.49*	0.59
Reason for drug relapsing:
Peers’ pressure and enticement	212	(58.2)	1.71**	1.22*
Desire, craving for drug	247	(67.9)	1.14	1.55**
Sad and disappointed	164	(45.1)	1.12	0.92
History of overdose	75	(20.3)	1.13	1.06
II. Family
Have economic dependents	10	(2.7)	1.30	0.40**
Cohabitants:
Parents	316	(85.4)	0.70*	1.08
Husband or wife	100	(27.0)	0.81	0.63**
Children	99	(26.8)	0.94	0.59**
Sibling	213	(57.6)	0.88	1.19
Relatives	44	(11.9)	0.64*	1.07
Partners	13	(3.5)	1.86*	1.26
Alone	4	(1.1)	0.96	n/a

Note: * p<0.3; ** p<0.05; ***p<0.01.

^aOdd ratio of higher income,

^bMillion Vietnamese dong in 2009 (1 USD = 17,800 dong).

n/a: not applicable.