Table 3.

Factors associated with syphilis seroconversion among HIV-infected patients (n=1010)

Baseline risk factor	Univariate IRR (95% CI)	p	Multivariate IRR (95% CI)	p
HIV exposure
Heterosexual	1		1
MSM	5.50 (2.96–10.22)	<0.001	3.48 (1.88–6.47)	<0.001
Injecting drug use	1.61 (0.21–12.52)	0.649
Other	3.39 (1.57–7.34)	0.002	2.50 (1.16–5.42)	0.02
Past syphilis diagnosis
No	1		1
Yes	6.06 (4.37–8.39)	<0.001	5.15 (3.69–7.17)	<0.001
Age, every 10-year increase	0.83 (0.70–0.98)	0.029	0.84 (0.71–1.00)	0.047
Sex
Male	1
Female	0.07 (0.01–0.54)	0.01
Prior AIDS diagnosis
Not known	1
Yes	0.76 (0.54–1.09)	0.134
CD4 cell count (cells/mm3)
≥500	1
350–499	1.14 (0.75–1.73)	0.549
200–349	0.94 (0.61–1.44)	0.775
<200	1.19 (0.71–1.98)	0.515
HIV viral load (copies/ml)
<400	1
≥400	0.94 (0.65–1.36)	0.742
Time after HIV diagnosis
Every one-year increase	1.02 (0.98–1.06)	0.295
Using HAART
Yes	1
No	0.88 (0.56–1.39)	0.593
HBsAg status
Negative	1
Positive	1.34 (0.84–2.14)	0.223
Hepatitis C antibody status
Negative	1
Positive	0.95 (0.44–2.05)	0.888

CI, confidence interval; IRR, incidence rate ratio; MSM, men who have sex with men; HAART, highly active antiretroviral therapy; HBsAg, hepatitis B surface antigen.

All models were adjusted for study site, though incident rate ratios for sites are not shown.