Table 3.

Logistic regression models^* to identify the determinants of hepatitis B core antibodies, hepatitis C antibodies, and HIV antibodies in injecting drug users entering Irish prisons

	Total No of prisoners (n=173)†	No (%) of prisoners positive for antibodies	Odds ratio (95% CI)	P value‡
Hepatitis B core antibodies (n=31)
Age (years):
< 30	143	21 (14.7)	1
⩾30	28	9 (32.1)	5.1 (1.7 to 15.3)	<0.01
Sex:
Male	147	23 (15.7)	1
Female	26	8 (30.8)	2.7 (0.8 to 8.3)	0.1
No of heterosexual partners in past year:
1-2	103	17 (16.5)	1
3-10	42	6 (14.3)	1.2 (0.4 to 3.8)	0.7
>10	10	4 (40.0)	6.0 (1.3 to 26.1)	0.02
None	12
Hepatitis C antibodies (n=124)
Sex:
Male	147	101 (68.7)	1
Female	26	46 (88.5)	3.5 (1.2 to 34.4)	0.05
No of times injected drugs in past month:
0	47	24 (51.1)	1
1-19	35	24 (68.6)	3.0 (1.0 to 9.4)	0.05
>19	85	72 (84.7)	6.3 (2.5 to 17.2)	<0.001
Shared needles in prison:
No	94	59 (62.8)	1
Yes	63	58 (92.1)	6.3 (2.3 to 20.3)	<0.001
First time in prison	14
HIV antibodies (n=10)
Age (years):
<30	143	5 (3.5)	1
⩾30	28	5 (17.9)	8.0 (1.9 to 37.6)	<0.01
Sex:
Male	147	6 (4.1)	1
Female	26	4 (15.4)	3.6 (0.8 to 16.8)	0.1
Shared needles in month before imprisonment:
No	118	3 (2.5)	1
Yes	52	7 (13.5)	5.9 (1.4 to 31.5)	0.02

^*Initial models included the variables age, sex, ever imprisoned, time spent in prison in preceding 10 years, tattooing, smoking heroin, length of time since first injection, started injecting in prison, sharing needles inside and outside prison, injecting frequency in prison, ever had sex with a man inside or outside prison, ever treated for a sexually transmitted infection, number of heterosexual partners, use of condoms during heterosexual intercourse, ever been paid for sex. Significant factors were retained in the final model. 

^†Numbers may not add up to total because not all respondents answered all questions. 

^‡For whole model for hepatitis B, χ²=13.8, P<0.01; for hepatitis C, χ²=36.6, P<0.0001; and for HIV, χ²=16.8, P<0.001.