Table 1

Incidence of hepatitis C among injecting drug users in Dublin, by general and drug misuse characteristics

	Number	Seroconvertors	Person years at risk (PYAR)	Incidence (per 100 PYAR)	95% Confidence intervals*	p Value†
*Confidence intervals for the incidence rate were calculated using the exact confidence limits for a Poisson count. †p Values were generated by comparing incidence rates using the z test. ‡Benzodiazepines were the principal drug injected in three cases. §Benzodiazepine misuse was determined on the basis of urine toxicology (Immunoassay EMIT test).
Total	100	67	101.6	66	51 to 84
Gender
Male	66	44	63.0	70	51 to 94
Female	34	23	38.6	60	38 to 89	0.54
Age ,(y)
Under 21	57	39	59.4	66	47 to 90
≥21	43	28	42.3	66	44 to 96	0.98
Employment
Unemployed	88	63	89.5	70	54 to 90
Working (or at school)	12	4	12.2	33	9 to 84	0.13
Current sexual relationship
No partner/non-injecting partner	68	45	70.5	64	47 to 85
Partner injects	29	20	26.9	74	45 to 115	0.57
Unknown	3	2	4.2	48	5.8 to 172.0
Imprisoned before first test
No	55	35	65.1	54	37 to 75
Yes	36	25	26.9	93	60 to 137	0.03
Unknown	9	7	9.7	72	29 to 149
Time since onset of injecting (months)
1 to 12	67	47	63.6	74	54 to 98
13 or more	33	20	37.7	53	32 to 82	0.21
Principal drug injected
Heroin	72	45	75.8	59	43 to 79
Other or combination	28	22	25.9	85	53 to 129	0.17
Daily drug expenditure
Up to Ir£65	76	48	80.4	60	44 to 79
More than Ir£65	24	19	21.0	90	54 to 141	0.12
Route of opioid use‡ at first testing
Not all injected	18	7	27.1	26	10 to 56
All injected	67	50	53.6	93	69 to 123	0.006
Unknown	15	10	21.0	48	23 to 88
Benzodiazepine misuse§
No	50	33	55.3	60	41 to 84
Yes	45	29	40.3	72	48 to 103	0.46
Unknown	5	5	6.0	83	27 to 194
Imprisoned between tests
No	77	48	69.1	69	51 to 92
Yes	15	12	21.9	55	28 to 96	0.46
Unknown	8	7	10.7	65	26 to 135
Addiction treatment between tests
None or less than 3 months treatment	67	42	56.2	75	54 to 101
More than 3 months	31	23	44.4	52	33 to 78	0.16
Unknown	2	2	1.1	182	22 to 657