Lesbians may be at higher risk of cervical cancer because they get fewer screenings than heterosexual women, due partly to doctors' sometimes incorrect assumptions about their sexual history, University of Washington researchers said on Tuesday. 

Although nearly all cases of cervical cancer are attributable to a human papillomavirus, or HPV, infection, healthcare providers often do not encourage lesbian patients to get regular HPV screenings, the researchers found.

That is because the disease is most commonly transmitted during heterosexual sex and doctors may wrongly assume lesbians have only had sex with other women, despite studies that have found most lesbians and their partners have had sex with men, researchers said.

A lack of testing can also occur at times because lesbians lack insurance or do not always have a need for pregnancy prevention checkups, or may not want to share their sexual orientation with doctors, the researchers said.

"If we are serious about reducing the rates of cervical cancer in lesbians, an unbiased health assessment by a provider must ask the question: 'Do you have sex with men, women or both?'" University of Washington School of Nursing professor Joachim Voss said in a statement.

Voss and Lindsay Waterman, an adult nurse practitioner at the Seattle-based university, analyzed medical literature and studies, including Pap screen rates, between 2000 and 2013, published in last month's Nurse Practitioner journal.

"Ob-gyns should provide the same comprehensive gynecologic health care to lesbians and bisexual women as they do to heterosexual women, including Pap tests," the American College of Obstetricians and Gynecologists has said.

Researchers were unable to quantify the overall rates of cervical cancer among lesbians compared with heterosexual women because cancer patients are not typically asked their sexual orientation, Voss said.

Screening every three years can detect abnormal cervical cells and pre-cancerous lesions in women ages 21 to 65, but lesbians are screened at rates 5 percent to 18 percent lower than heterosexual women because of the perceived lack of risk exposure, the researchers said.

HPV can be transmitted between women partners through both skin-to-skin contact and contact with sex toys.

Nearly eight of every 100,000 U.S. women are diagnosed with cervical cancer annually, the researchers said.