Table 4.

Factors associated with phylogenetic pair/cluster membership among people who inject drugs in Vancouver, Canada.

Characteristic	No cluster (n=591)	Cluster (n=108)	p-value	Unadjusted OR (95% CI)	p-value	Adjusted OR (95% CI)	p-value
Age quartiles			0.005
<27	123 (21%)	27 (25%)		2.20 (1.17, 4.12)	0.014	3.14 (1.54, 6.39)	0.002
27 – 34	155 (26%)	42 (39%)		2.71 (1.51, 4.85)	0.001	2.70 (1.48, 4.91)	0.001
35 – 39	123 (21%)	20 (19%)		1.63 (0.83, 3.17)	0.154	1.74 (0.88, 3.44)	0.108
>40	190 (32%)	19 (18%)		1.00	-	1.00	-
Female (vs. Male)	149 (25%)	30 (28%)	0.574	1.14 (0.72, 1.81)	0.574	0.87 (0.53, 1.41)	0.564
Duration injecting (years)			<0.001
<3	55 (9%)	23 (21%)		4.45 (2.26, 8.75)	<0.001
3-10	172 (29%)	41 (38%)		2.53 (1.42, 4.53)	0.002
10-20	162 (27%)	25 (23%)		1.64 (0.87, 3.08)	0.124
>20	202 (34%)	19 (18%)		1.00	-
ARYS Cohort (vs. VIDUS)	58 (10%)	7 (6%)	0.273	0.64 (0.28, 1.44)	0.277	0.39 (0.15, 1.00)	0.049
Recent HCV seroconversion (vs. HCV infection at baseline)	60 (10%)	13 (12%)	0.556	1.21 (0.64, 2.29)	0.556	1.45 (0.72, 2.93)	0.302
HIV co-infection (vs. not)	128 (22%)	37 (34%)	0.005	1.89 (1.21, 2.94)	0.005	1.97 (1.22, 3.18)	0.005
HCV subtype			0.039
1a	307 (52%)	40 (37%)		1.00	-	1.00	-
1b	36 (6%)	8 (7%)		1.71 (0.74, 3.93)	0.21	2.13 (0.90, 5.03)	0.086
2b	43 (7%)	9 (8%)		1.61 (0.73, 3.54)	0.24	1.67 (0.75, 3.76)	0.212
3a	205 (35%)	51 (47%)		1.91 (1.22, 2.99)	0.005	2.12 (1.33, 3.38)	0.002

Note: Participants were classified as in a cluster if the time to most common recent ancestor of a potential cluster was less than five years

OR: Odds ratio; CI: Confidence interval; ARYS: At-Risk Youth Study; VIDUS: Vancouver Injection Drug User Study

Full model adjusted for age, sex, cohort of enrolment, recent HCV seroconversion, HIV infection, and HCV subtype;