[attach id=245149 size="medium" align="left"]Pap smears have picked up abnormalities that helped find problems farther up the cervix that could lead to cancer.[/attach]

Certain types of abnormalities that can lead to cervical cancer may be missed when young women go years between Pap smears, according to a US study.

Last year, the government-backed US Preventive Services Task Force said women under 21 don’t need to be screened for cervical cancer and Pap smears can be done once every three years after that – guidelines that broadly agree with others released by groups such as the American Cancer Society.

Lisa Barroilhet, at the University of Wisconsin Hospital in Madison and the study’s lead author, told Reuters Health that she agrees with those recommendations and her findings are not a reason to change them.

But Pap smears have picked up abnormalities that helped find problems farther up the cervix that could lead to cancer, she said.

Barroilhet and her team reviewed the records of 242 women with adenocarcinoma in situ (AIS) – cervical abnormalities that can lead to adenocarcinoma, one form of cervical cancer. Those cancers occur further up the cervix than the squamous cell carcinomas typically caught by Pap smears, so they’re not a focus of Pap-related guidelines, she added.

However, she and her colleagues found most young women in the study were diagnosed with AIS because of other abnormal lesions picked up on Pap smears that led to more testing and biopsies.

That was the case for 16 of the 17 women diagnosed with AIS before age 21, they wrote in Obstetrics & Gynaecology.

Even though Pap smears weren’t designed to catch adenocarcinoma precursors, the findings mean less-frequent Pap smears could lead to more of those full-on cancers developing, Barroilhet said. That’s especially a concern because they can be a faster-growing type of cancer.

But Rebecca Horvat, a pathologist from the University of Kansas Medical Centre representing the American Society for Clinical Pathology, said most abnormal lesions still take years to develop into adenocarcinomas.

“It doesn’t do (that), as soon as you get it, you get a cancer,” said Horvat, who wasn’t involved in the new study. “It can be easily picked up every three years.”

She said the main challenge with moving to screening every three years may be a psychological one for women who have spent years getting an annual Pap smear.

Because both adenocarcinomas and squamous cell carcinomas can be caused by human papillomavirus, or HPV, Barroilhet said preventing the infection remains a public health priority.

“The best way to prevent any of this is HPV vaccination,” she said.