High incidence of diagnosis with syphilis co-infection among men who have sex with men in an HIV cohort in Ontario, Canada.
BACKGROUND
The re-emergence of syphilis among HIV-positive gay and other men who have sex with men (MSM) requires vigilance. We estimated incidence of and risk factors for first and subsequent syphilis diagnoses among MSM in HIV care in Ontario, Canada.


METHODS
We analyzed data from 2,280 MSM under follow-up from 2006 to 2010 in the Ontario HIV Treatment Network Cohort Study (OCS), a multi-site clinical cohort. We obtained syphilis serology results via record linkage with the provincial public health laboratory. Rates were calculated using Poisson regression.


RESULTS
First syphilis diagnoses occurred at a rate of 2.0 per 100 person-years (95 % CI 1.7, 2.4; 121 cases) whereas the re-diagnosis rate was 7.5 per 100 person-years (95 % CI 6.3, 8.8; 136 cases). We observed higher rates over time and among men who were aged <30 years, receiving care in the two largest urban centers, or had a previous syphilis diagnosis. Syphilis diagnosis was less common among Indigenous men, men with higher CD4 cell counts, and, for first diagnoses only, among men with less than high school education.


CONCLUSIONS
Compared to reported cases in the general male population, incidence of a new syphilis diagnosis was over 300 times greater among HIV-positive MSM but year-to-year changes reflected provincial trends. Re-diagnosis was common, suggesting treatment failure or re-infection. Novel syphilis control efforts are needed among HIV-positive MSM.
Ontario HIV Treatment Network, Suite 600, 1300 Yonge Street, Toronto, ON, M4T 1X3, Canada. ann.burchell@utoronto.ca.|Dalla Lana School of Public Health, University of Toronto, Toronto, Canada. ann.burchell@utoronto.ca.|Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Canada. ann.burchell@utoronto.ca.|Department of Family and Community Medicine, St. Michael's Hospital, Toronto, Canada. ann.burchell@utoronto.ca.
Ann N
AN
Burchell
Public Health Laboratories, Public Health Ontario, Toronto, Canada. vanessa.allen@oahpp.ca.
Vanessa G
VG
Allen
Ontario HIV Treatment Network, Suite 600, 1300 Yonge Street, Toronto, ON, M4T 1X3, Canada. sgardner@ohtn.on.ca.|Dalla Lana School of Public Health, University of Toronto, Toronto, Canada. sgardner@ohtn.on.ca.
Sandra L
SL
Gardner
Ontario HIV Treatment Network, Suite 600, 1300 Yonge Street, Toronto, ON, M4T 1X3, Canada. vmoravan@ohtn.on.ca.
Veronika
V
Moravan
Department of Medicine, University of Toronto, Toronto, Canada. darrell.tan@gmail.com.|Toronto General Research Institute, University Health Network, Toronto, Canada. darrell.tan@gmail.com.|Division of Infectious Diseases, St. Michael's Hospital, Toronto, Canada. darrell.tan@gmail.com.
Darrell H S
DH
Tan
Ontario HIV Treatment Network, Suite 600, 1300 Yonge Street, Toronto, ON, M4T 1X3, Canada. rgrewal@ohtn.on.ca.
Ramandip
R
Grewal
Dalla Lana School of Public Health, University of Toronto, Toronto, Canada. jraboud@uhnresearch.ca.|Toronto General Research Institute, University Health Network, Toronto, Canada. jraboud@uhnresearch.ca.
Janet
J
Raboud
Department of Medicine, University of Toronto, Toronto, Canada. ahmed.bayoumi@utoronto.ca.|Institute of Health Policy, Management and Evaluation, University of Toronto, Toronto, Canada. ahmed.bayoumi@utoronto.ca.|Division of General Internal Medicine, St. Michael's Hospital, Toronto, Canada. ahmed.bayoumi@utoronto.ca.|Centre for Research on Inner City Health, Li KaShing Knowledge Institute, St. Michael's Hospital, Toronto, Canada. ahmed.bayoumi@utoronto.ca.
Ahmed M
AM
Bayoumi
Department of Medicine, University of Toronto, Toronto, Canada. rupert.kaul@utoronto.ca.
Rupert
R
Kaul
Public Health Laboratories, Public Health Ontario, Toronto, Canada. tony.mazzulli@oahpp.ca.|Mount Sinai Hospital, Toronto, Canada. tony.mazzulli@oahpp.ca.
Tony
T
Mazzulli
AIDS Bureau, Ontario Ministry of Health and Long Term Care, Toronto, Canada. frank.mcgee@ontario.ca.
Frank
F
McGee
Ontario HIV Treatment Network, Suite 600, 1300 Yonge Street, Toronto, ON, M4T 1X3, Canada. sean.rourke@utoronto.ca.|Department of Psychiatry, University of Toronto, Toronto, Canada. sean.rourke@utoronto.ca.|Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Canada. sean.rourke@utoronto.ca.
Sean B
SB
Rourke
D000328:Adult; D000368:Aged; D015331:Cohort Studies; D060085:Coinfection; D015658:HIV Infections / Q000150:complications*; D018451:Homosexuality, Male; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009864:Ontario / Q000453:epidemiology; D012307:Risk Factors; D013587:Syphilis / Q000097:blood / Q000150:complications / Q000453:epidemiology*; D013588:Syphilis Serodiagnosis