Women who have never had a Pap test are almost three times as likely to be diagnosed with a deadly form of cervical cancer as women who have regularly undergone the simple gynecological test, a new Canadian study shows.
While the research, published in the medical journal Open Medicine, demonstrates the value of the screening test, it also sheds light on the barriers to testing.
The researchers, led by Kathleen Decker of CancerCare Manitoba, found that women in that province had, on average, about 18 opportunities to have a Pap test over a five-year period.
Yet, among those diagnosed with an advanced form of cervical cancer, 54 per cent had not undergone a Pap test in the previous five years, compared with 33 per cent of women in the general population. Moreover, one in four women had never had a Pap test.
The research team found that "lack of continuity of care" was the principal reason for the low rate of screening - meaning that women who see a doctor only when they have an acute health problem are most likely to fall through the cracks.
"A steady relationship between continuity of care and better preventive health care has been observed," Ms. Decker and her team wrote. (The researchers were not available to be interviewed because they were unable to get prompt permission from CancerCare Manitoba.)
But a number of other factors also came into play:
Women who were seen routinely by a gynecologist or obstetrician (as opposed to a family doctor) were more likely to get a Pap test;
Female doctors were markedly more likely than male doctors to do Pap testing;
Doctors practising in rural areas were less likely to do the screening than those working in urban areas;
Canadian-educated doctors performed Pap tests at a higher rate than foreign-trained physicians;
The lower a woman's family income, the less likely she was to be tested.
Researchers were unable to determine, based on the records, when physicians failed to offer the Pap test and when women refused it.
The study involved 4,009 Manitoba women, including 666 who were diagnosed with invasive cervical cancer and 3,343 others of similar background who served as a control group. The average age for the cancer diagnosis was 50.
The researchers said that, based on the data, initiation to Pap testing is crucial because, once a women has undergone a test, she is far more likely to do so routinely.
The Pap test was developed in the 1920s by pathologist George Papanicolaou. It involves the examination of a sample of cells scraped from the cervix to detect cancerous and pre-cancerous lesions.
Routine testing of women has resulted in a dramatic reduction in mortality from cervical cancer.
In 2009, about 1,300 Canadian women will be diagnosed with cervical cancer and 380 will die of the disease, according to the Canadian Cancer Society.
The main cause of cervical cancer is persistent infection of the cervix with a high-risk strain of the human papillomavirus. HPV is a virus that is transmitted through sexual contact. It is common among both women and men. In recent years, pre-teen and teenaged girls in Canada have been vaccinated against HPV infection.
The Canadian Cancer Society recommends that women who are or have been sexually active have a regular Pap test and pelvic examination, even if no longer having sex, and even if they have been vaccinated.