Ontario intervention increases detection of syphilis

Over the past 20 years in Canada and other high-income countries, rates of new diagnoses of syphilis have increased among gay, bisexual and other men who have sex with men (MSM), including some who are HIV positive.

Syphilis can cause a complex multistage disease, affecting many organ-systems. Because syphilis is a relatively common sexually transmitted infection (STI), sexually active people need regular screening. Early detection and treatment can help ensure that complications relating to syphilis are minimized and that the disease does not spread.

A team of leading researchers in Ontario conducted a study among four large HIV clinics in Toronto and Ottawa, cities with relatively high rates of syphilis. The researchers compared two interventions in their study:

  • Whenever HIV-positive men gave blood samples to assess their viral loads, syphilis screening was also done.
  • The usual syphilis testing practices were done—that is, screening for syphilis was triggered by the patient reporting (or the doctor noticing) signs/symptoms typical of syphilis; a request for such testing by the doctor or patient; the patient disclosing to their physician sexual activity that warranted testing, and so on.

The study was done between February 2015 and July 2017. During this time, all four clinics initially engaged in the usual syphilis testing practices; gradually, over the course of the study, one clinic at a time shifted to screening for syphilis whenever HIV viral load testing was done.

Nearly 4,000 men with HIV took part in the study.

Over the course of the study the following occurred:

  • There was a 25% increase in detection of early-stage syphilis.
  • On average, each participant had at least two syphilis tests each year.
  • The number of patients who received a syphilis test at least once per year increased fourfold.

Having syphilis screening as a routine part of testing was perceived by participants as a good thing for the following reasons:

  • convenience
  • reduced stigma around STIs
  • reduced risk of missed opportunities for syphilis screening

For the future

Computer simulations suggest that syphilis screening every three months would likely improve the ability of doctors and nurses to detect cases of early syphilis and interrupt transmission of the germ that causes syphilis. The present study was not designed to elicit such frequent testing, but it has started doctors and their HIV-positive patients on the path toward regular syphilis testing. According to the Ontario team of researchers, in order to achieve syphilis screening every three months, additional interventions will be required, including the following:

  • “improved diagnostics that allow for self-testing”
  • “virtual and express testing” – patients can obtain lab requisition forms for syphilis testing via a smartphone or computer rather than having to first visit a doctor
  • reminders that are sent to patients about the need for frequent testing

—Sean R. Hosein


  1. Burchell AN, Tan DHS, Grewal R, et al. Routinized syphilis screening among men living with human immunodeficiency virus: A stepped wedge cluster randomized controlled trial. Clinical Infectious Diseases. 2022 Mar 9;74(5):846-853. 
  2. Aho J, Lybeck C, Tetteh A, et al. Rising syphilis rates in Canada, 2011-2020. Canada Communicable Disease Report. Feb/Mar 2022; 48(2,3): 52.