Changes made in 2012 to Canada's screening guidelines for cervical cancer – effectively eliminating the need for women under 21 to get annual Pap tests – have contributed to a rise in chlamydia cases among young females in Ontario, according to a new study.
Historically, doctors have done Pap tests and chlamydia tests at the same time. But with women under 21 not recommended to have Pap checkups, testing for chlamydia fell, leading to an increase in cases of the world's most commonly diagnosed sexually transmitted infection (STI). Over the age of 21, Pap tests are recommended every three years.
Left untreated, chlamydia can lead to pelvic inflammatory disease, ectopic pregnancy and infertility.
The report found that, two years after the Canadian Task Force on Preventive Health Care changes to cervical-cancer screening guidelines, chlamydia testing in women aged 15 to 19 dropped 26 per cent, and 18 per cent in women aged 20 to 24.
During the same period, chlamydia cases fell 17 per cent in women aged 15 to 19, and 14 per cent in women aged 20 to 24.
The researchers of the report published Monday in the Annals of Family Medicine estimate that over 2,700 fewer cases of chlamydia were detected per year in Ontario, for the two years following the guideline change.
"The decrease in incidence is a false comfort," says the report's co-author Dr. Jeff Kwong, a senior scientist with the Institute for Clinical Evaluative Sciences (ICES). "The data suggests there are more women infected [with chlamydia] that we are just not detecting. So the greatest concern is that there are all these women out there who don't know they have an infection, having sex, and spreading it to others," says Kwong.
Public Health Ontario data shows the incidence of chlamydia infection has increased, with cases totalling 41,829 cases in 2016 in Ontario, compared with 39,037 cases in 2015; 35,987 in 2014, and 34,684 in 2013.
In 2006, there were 22,409 reported chlamydia cases in the province.
Sexually active teens are at greatest risk of chlamydia infection.
The new report looked at all females and males aged 15 to 29 years of age based on data from physician billing claims through OHIP (Ontario Health Insurance Plan) and public-health surveillance figures from 2010 to 2014 – two years before, and two years after, the guideline changes. Males were included as a comparison, since the changes were not expected to have much impact on them.
Dr. Gabriela Lewin, a member of the Canada cervical cancer guideline working group, says her team anticipated eliminating yearly Pap tests could impact screening for chlamydia and other STIs. "We are going to update the guidelines for chlamydia screening, and [we] have a working group already set up." She expects the new protocol will be done in two years.
"We will see if annual chlamydia testing is worth it for everybody or just in the high-risk populations … and whether it's when younger women come in for contraception or any other reason," says Lewin, vice-chair of the Canadian Task Force on Preventive Health Care.
Still, she said there are "limitations" to looking at only one data base, ie. Ontario, and reviewing data, retrospectively. (All the other provinces follow the same basic cervical-cancer screening guidelines.)
That aside, Lewin stressed it's important "to put on the radar we've left out this population of young ladies. We don't need to do annual cervical cancer screening, but perhaps [we should] offer yearly chlamydia screening for this age group."
Kwong, who co-authored the report with Dr. Michelle Naimer, clinical director of the Mount Sinai Academic Family Health Team, would like to see separate screening recommendations for STIs and cervical cancer. He says sexually active women under the age of 25 should be screened once a year – perhaps twice a year if they have multiple sexual partners – particularly new ones.
"It's ironic that testing for chlamydia [often just a urine test, rather than a swab] is easier than it used to be. But we're not doing it, because awareness is so low."