30 October 2014 

Ontario researchers call for more STI testing, particularly among gay and bisexual men

Common sexually transmitted infections (STIs)—such as herpes, chlamydia, gonorrhea, syphilis, human papilloma virus (HPV)—can cause inflammation and/or sores on, around or inside the wet delicate tissue lining the anus, mouth/throat, penis and vagina. In some cases, the inflammation and/or sores may be painless, so affected people may not notice them and so not seek care.

The inflammation caused by STIs may make some people more susceptible to HIV infection.

Among people who already have HIV, STIs can be a problem for at least the following reasons:

  • They weaken the immune system and increase the risk of getting other STIs.
  • They increase the production of HIV and thereby increase the risk of spreading HIV.
  • Germs such as syphilis can quickly spread to vital organs, including the brain.
  • There has been an increase in difficult-to-treat strains of gonorrhea and such infections can be extremely unpleasant.

Many common STIs—herpes, chlamydia, gonorrhea, syphilis and HPV—can be spread through condomless oral, vaginal and anal sex.

Thus, regular (and in some cases frequent) medical checkups and screening for STIs are necessary for sexually active adults, particularly those who have anonymous sex and/or multiple sex partners. Correct and consistent use of condoms is also helpful in providing protection from many STIs.

Increasing infections

For at least the past decade, cases of syphilis and HIV have been rising among gay and bisexual men in Canada and other high-income countries. Indeed, reports from Canada suggest that cases of syphilis have risen at least 10-fold in that time, particularly among men who have sex with men (MSM).

Researchers at the Ontario HIV Treatment Network (OHTN) have collaborated with leading HIV clinics in this province to study syphilis testing. The researchers found that rates of such testing, though increasing, were less than ideal. To remedy this situation, they have suggestions for both clinics and patients to ensure that more patients are screened and more STIs are detected and treated so that their spread can decrease.

Study details

The Ontario Cohort Study (OCS) collects health-related information from 12 HIV clinics across the province. Participants who volunteered for the study also completed questionnaires and since 2008 underwent annual interviews. Researchers analysed data from 4,232 participants collected between the years 2000 and 2009.

The scientists sought and obtained information about syphilis testing by communicating with the Public Health Ontario Laboratories. These labs provide syphilis testing for the entire province. The sequence of syphilis testing in Ontario is as follows:

  • Blood samples are first run through an automated analyser called the Abbott Architect (this checks for antibodies to syphilis).
  • If the Architect test result is positive, then confirmatory screening is done with a second test—RPR (rapid plasma reagin), TPPA (Treponema pallidum particle agglutination test) or FTA-ABS (fluorescent treponemal antibody absorbed test). These secondary tests measure antibodies that attack fatty molecules released from cells damaged by the germ (T. pallidum) that causes syphilis or, in some cases, from T. pallidum itself.

Researchers at Ontario’s public health labs think that this sequence of screening is likely to detect early syphilis cases better than previous algorithms.

The basic profile of participants was as follows:

  • average age – 45 years
  • 86% men, 14% women
  • average CD4+ cell count – 455 cells/mm3


Scientists found that 4,232 participants had 7,313 syphilis tests during the nine-year study period.

Among different populations, the proportion of people who tested for syphilis was as follows:

  • MSM – 84%
  • women – 78%
  • straight men – 75%

Most (86%) syphilis test requests were done by doctors and nurses in HIV clinics. The scientists noted: “Overall, 77% of syphilis tests were ordered [at the same time as HIV viral load tests].”

Testing patterns

Over the course of the study, researchers found that rates of syphilis testing had increased markedly. For instance, in the year 2000 only about 3% of participants had a syphilis test. By the year 2009, about 55% of participants had a syphilis test.

This increase in testing is an improvement over earlier years. However, it is still less than ideal.

Test results

Based on the results of testing, the research team estimated that over the lifetime of HIV-positive patients in Ontario “at least one in five” will have syphilis.

In 2009, the researchers found that at least 4% of MSM in their study had a new case of syphilis.

Other studies in Western Europe and Australia have found broadly similar rates of syphilis in MSM, particularly HIV-positive MSM, as in the Ontario study.

Bear in mind that due to issues related to the design of the study, it is extremely likely that the research team underestimated the cases of syphilis in HIV-positive MSM in Ontario.

Key points

  • Cases of syphilis have increased in many regions since the year 2000, in some cases by at least tenfold.
  • According to Ontario researchers, “the vast majority of [syphilis cases are] among MSM, many of whom are co-infected with HIV.”
  • Although rates of syphilis testing have increased over time, they are still less than ideal.
  • The researchers stated that they “…recommend that future efforts to improve timely detection and treatment of syphilis in [HIV-positive MSM] include systematic and operational changes to health care practice, such as clinic-based interventions.”
  • The study’s findings underscore the need for sexually active adults, particularly gay and bisexual men, to have regular, and in some cases frequent, medical checkups and screening for STIs and prompt treatment when such STIs are diagnosed. Sexually active adults can reduce their risk for STIs by consistent and correct use of condoms.


Syphilis – CATIE fact sheet

What the syph is going on? Responding to syphilis outbreaks in CanadaPrevention in Focus

Management and Treatment of Specific Infections: SyphilisCanadian Guidelines on Sexually Transmitted Infections

Pharmacological treatment STBBI: Syphilis – L’Institut national d’excellence en santé et en services sociaux (INESSS)

New information for gay men living-with HIV: STI testing is good for your health – Ontario HIV Treatment Network

—Sean R. Hosein


  1. Lukehart SA, Hook EW 3rd, Baker-Zander SA et al. Invasion of the central nervous system by Treponema pallidum: implications for diagnosis and treatment. Annals of Internal Medicine. 1988 Dec 1;109(11):855–62.
  2. Ghanem KG, Moore RD, Rompalo AM, et al. Lumbar puncture in HIV-infected patients with syphilis and no neurologic symptoms. Clinical Infectious Diseases. 2009 Mar 15;48(6):816-21.
  3. Sullivan PS, Hamouda O, Delpech V, et al. Reemergence of the HIV epidemic among men who have sex with men in North America, Western Europe and Australia, 1996-2005. Annals of Epidemiology. 2009 Jun;19(6):423-31.
  4. Leber A, MacPherson P, Lee BC. Epidemiology of infectious syphilis in Ottawa. Recurring themes revisited. Canadian Journal of Public Health. 2008 Sep-Oct;99(5):401-5.
  5. Dumaresq J, Langevin S, Gagnon S, et al. Clinical prediction and diagnosis of neurosyphilis in HIV-infected patients with early Syphilis. Journal of Clinical Microbiology. 2013 Dec;51(12):4060-6.
  6. Kofoed K, Gerstoft J, Mathiesen LR, et al. Syphilis and human immunodeficiency virus (HIV)-1 coinfection: influence on CD4 T-cell count, HIV-1 viral load, and treatment response. Sexually Transmitted Diseases. 2006 Mar;33(3):143-8.
  7. Goswami ND, Stout JE, Miller WC, et al. The footprint of old syphilis: using a reverse screening algorithm for syphilis testing in a U.S. Geographic Information Systems-Based Community Outreach Program. Sexually Transmitted Diseases. 2013 Nov;40(11):839-41.
  8. Gratrix J, Plitt S, Lee BE, et al. Impact of reverse sequence syphilis screening on new diagnoses of late latent syphilis in Edmonton, Canada. Sexually Transmitted Diseases. 2012 Jul;39(7):528-30.
  9. Sellati TJ, Wilkinson DA, Sheffield JS, et al. Virulent Treponema pallidum, lipoprotein, and synthetic lipopeptides induce CCR5 on human monocytes and enhance their susceptibility to infection by human immunodeficiency virus type 1. Journal of Infectious Diseases. 2000 Jan;181(1):283-93.
  10. Ghanem KG, Moore RD, Rompalo AM, et al. Neurosyphilis in a clinical cohort of HIV-1-infected patients. AIDS. 2008 Jun 19;22(10):1145-51.
  11. Tuite AR, Burchell AN, Fisman DN. Cost-effectiveness of enhanced syphilis screening among HIV-positive men who have sex with men: a microsimulation model. PLoS One. 2014 Jul 1;9(7):e101240.
  12. Burchell AN, Allen VG, Moravan V, et al. Patterns of syphilis testing in a large cohort of HIV patients in Ontario, Canada, 2000-2009. BMC Infectious Diseases. 2013 May 28;13:246.
  13. Mulhall BP, Wright S, Allen D, et al. High rates of sexually transmissible infections in HIV-positive patients in the Australian HIV Observational Database: a prospective cohort study. Sexual Health. 2014 Sep;11(4):291-7.
  14. Giard M, Queyron PC, Ritter J, et al. The recent increase of syphilis cases in Lyon University hospitals is mainly observed in HIV-infected patients: descriptive data from a laboratory-based surveillance system. Journal of Acquired Immune Deficiency Syndromes. 2003 Dec 1;34(4):441-3.
  15. Spornraft-Ragaller P, Boashie U, Stephan V, et al. Analysis of risk factors for late presentation in a cohort of HIV-infected patients in Dresden: positive serology for syphilis in MSM is a determinant for earlier HIV diagnosis. Infection. 2013 Dec;41(6):1145-55.
  16. Jin F, Prestage GP, Zablotska I, et al. High incidence of syphilis in HIV-positive homosexual men: data from two community-based cohort studies. Sexual Health. 2009 Dec;6(4):281-4.
  17. Kelesidis T. The cross-talk between spirochetal and immunity. Frontiers in Immunology. 2014 Jun 30;5:310.