Table 3. Risk factor analysis for anti-HBc seroprevalence among first-time donors (N = 2799).

Variable			Bivariate analysis			Multivariable analysis
		n anti-HBc(+)/N total per group (%)	OR	95% CI	P-value	OR	95% CI	P-value
Age (years)	≤ 20	748/1856 (40.3)	ref			ref
	21–25	237/485 (48.9)	1.42	[1.2–1.7]	<0.001	1.5	[1.2–2.0]	<0.001
	26–30	121/224 (54.0)	1.74	[1.3–2.3]	<0.001	2.2	[1.5–3.2]	<0.001
	31–35	54/100 (54.0)	1.74	[1.2–2.6]	0.009	2.0	[1.2–3.3]	0.006
	≥ 36	73/134 (54.5)	1.77	[1.2–2.5]	0.001	2.3	[1.5–3.7]	<0.001
Sex	Female	334/934 (35.8)	ref			ref
	Male	899/1865 (48.2)	1.7	[1.7–1.4]	<0.001	1.5	[1.3–1.8]	<0.001
Occupation	Student	804/1958 (41.1)	ref			ref
	Office worker	60/189 (31.7)	0.7	[0.5–0.9]	0.013	0.5	[0.3–0.8]	0.002
	Soldier	226/432 (52.3)	1.6	[1.3–1.9]	<0.001	0.9	[0.7–1.3]	0.688
	Other	143/220 (65.0)	2.7	[2.0–3.6]	<0.001	0.9	[0.6–1.2]	0.410
Region	Centre	241/743 (32.4)	ref			ref
	South	210/805 (26.1)	0.7	[0.6–0.9]	0.006	0.7	[0.6–0.9]	0.003
	North	782/1251 (62.5)	3.5	[2.9–4.2]	<0.001	3.3	[2.6–4.0]	<0.001

OR = odds ratio; CI = confidence interval.