Changes to Pap testing lead to thousands of missed chlamydia cases: study

This photomicrograph shows cancerous cells detected by a Pap test. (THE CANADIAN PRESS/HO)

TORONTO -- Researchers say changes to Ontario's cervical cancer screening guidelines have led to thousands of women not being tested and diagnosed for chlamydia.

Chlamydia is the world's most common sexually transmitted disease; left untreated, the bacterial infection can lead to pelvic inflammatory disease, ectopic pregnancy and infertility.

Two years after Ontario's cervical cancer screening guidelines changed in 2012, chlamydia testing dropped 26 per cent in females aged 15 to 19 and 18 per cent in those aged 20 to 24 -- with more than 2,700 fewer cases being detected.

The new guidelines recommend that women who have been sexually active receive a Pap test every three years starting at age 21, instead of having one annually starting three years after becoming sexually active.

Doctors usually collect swabs to screen for sexually transmitted infections like chlamydia while doing a Pap test for cervical cancer.

The researchers hope greater public awareness about the need for young women to be tested for chlamydia and the availability of a simple urine test will lead to more screening.

"From a public health perspective, it is important to ensure that chlamydia cases are diagnosed in order to limit the spread of infection and the longer-term impacts of this infection if it isn't caught and treated," said co-author Dr. Jeff Kwong, a scientist at Public Health Ontario and the Institute for Clinical Evaluative Sciences.

"This is particularly true for women younger than 21 years of age who are at risk for chlamydia if they are sexually active and who no longer warrant cervical cancer screening," he said. "This research shows that women should be tested for chlamydia based on risk, regardless of the need for Pap tests."

The findings are published in the July 10 issue of the Annals of Family Medicine.