Table 2.

Incidence of hepatitis C virus infection among injecting drug users

Variable	Seroconversions	Total	Incidence per 100 person years (95% CI)	P value
Overall number	31	152	20.9 (13.5 to 28.3)
Sex:
Men	15	63	26.2 (13.0 to 39.5)
Women	14	85	15.9 (7.6 to 24.2)	0.18
Transsexual	2	4	70.3 (0.0 to 175.1)	0.19
Age at test (years):
<20	13	31	75.6 (34.5 to 116.8)
20-29	17	110	14.7 (7.7 to 21.6)	<0.0005
⩾30	1	11	6.6 (0.0 to 19.8)	0.02
Sexual preference:
Homosexual	10	33	32.6 (12.4 to 52.7)
Bisexual	5	35	12.6 (1.6 to 23.7)	0.08
Heterosexual	16	84	20.5 (10.5 to 30.6)	0.25
Duration of drug use (years):
<5	21	100	22.9 (13.1 to 32.8)
⩾5	10	51	17.9 (6.8 to 29.1)	0.52
Type of drug used:
Opiates only	6	29	19.2 (3.8 to 34.6)
Stimulants only	4	41	10.0 (2.5 to 19.9)	0.31
Multiple drugs	21	81	28.1 (16.1 to 40.1)	0.41
Shared equipment since last test:
No	9	80	11.9 (4.1 to 19.8)
Yes	22	72	30.2 (17.6 to 42.8)	0.02
Methadone treatment:
Ever	6	27	18.0 (3.6 to 32.4)
Never	20	117	18.0 (10.0 to 25.8)	0.99
History of imprisonment:
Yes	12	25	60.8 (26.4 to 95.2)
No	15	118	12.5 (6.2 to 18.8)	<0.0005
Study period:
2/92 to 12/93	12	91	18.9 (8.2 to 29.5)
1/94 to 10/95	19	125	22.5 (12.4 to 32.6)	0.63