Chlamydia testing for young women declines after revised Pap test guidelines

After Pap tests became less frequent in Canada, researchers found chlamydia tests also decreased, particularly among young women and teens. Doctors suggest young women should ask about testing for the sexually transmitted infection.

Doctors encourage sexually active women under 21 to ask for chlamydia test

An unintended consequence of delaying routine cervical cancer screening until age 21 is that testing for chlamydia has declined. (Craig Lassig/AP Images for College of American Pathologists)

After Pap tests became less frequent in Canada, testing for chlamydia also decreased, say researchers who recommend that young women should ask their doctors about testing for the sexually transmitted infection.

In May 2012, guidelines from Cancer Care Ontario recommended less frequent Pap tests for routine cervical cancer screening and delaying screening until age 21. The Canadian Task Force on Preventive Health Care suggested similar changes.

Chlamydia is the most commonly diagnosed bacterial sexually transmitted infection worldwide, according to public health authorities.  

Most women with chlamydia don't have symptoms and could unknowingly spread the infection. Left untreated, it can lead to upper genital tract infections or damage to fallopian tubes, leading to infertility as a complication.

Traditionally, women received chlamydia tests at the same time as cervical cancer screening. Dr. Jeff Kwong, a scientist at the Institute for Clinical Evaluative Sciences and Public Health Ontario, and his team wondered if the Pap guideline changes would affect Pap tests and chlamydia tests.

In Monday's online issue of the Annals of Family Medicine, the researchers write that an unintended consequence was chlamydia tests dropped 26 per cent among women aged 15 to 19 — the age group no longer in the Pap test guidelines.

In 2016, 41,829 cases of chlamydia were reported in Ontario.

The researchers estimated that 2,726 fewer cases of chlamydia were detected each year in Ontario following the guideline change.  

"That is quite a substantial number missed," said Kwong, who is also a family physician. "To have 3,000 women who are missed because of this is a little bit concerning."

The researchers also found that Pap testing itself also decreased as expected, based on an analysis of physician billing claims data and public health surveillance data. The declines occurred in all women up to age 29.

Kwong said women under 21 who aren't screened for cervical cancer "need to be proactive and ask to be tested for chlamydia if they're sexually active."

A urine sample is all that's needed to test for chlamydia.

In particular, people who have a new sexual partner or multiple partners in a relatively short time period are encouraged to be screened for sexually transmitted infections.

Not on all doctors' radar

The researchers also want to get the word out to doctors and nurses to think about chlamydia screening, especially for patients in high-risk groups.

"Old habits can sometimes be hard to break, so it may not be on their radar that they have to worried about STI screening separately from the cervical cancer screening."

For public health officials, the findings highlight the need to track if chlamydia infections are on the increase.

Kwong suspects the findings would likely be similar in other provinces, but only Ontario data was studied. A previous study of family medicine clinics at the University of Michigan also pointed to higher screening rates for chlamydia among females aged 15 to 21 before cervical cancer screening guidelines changed.

To increase chlamydia screening, the researchers suggested primary care clinics could provide urine collection cups at registration, send alerts to physicians, educate staff and offer self-collected vaginal swabs.

With files from CBC's Amina Zafar