Pap smears vs HPV testing: Out with old, in with the new?
ALMOST 100 years ago, Aurel Babeş in Romania and George Papanicolaou at Cornell University, two scientists without knowledge of a similar endeavour by the other, were evaluating the cervical cell changes in vaginal fluid. In 1926, Babeş introduced cytologic sampling for detecting cervical cancer and published his work in 1928. That same year, Papanicolaou presented his work on vaginal smears. Papanicolaou received more recognition for his work, and today we have the “Pap” smear and not the “Babeş” smear.
Fast-forward to 1988, when Harald zur Hausen demonstrated that cervical cancer is caused by certain types of papillomaviruses, and we know that 99.7 per cent of cervical cancer has human papilloma virus (HPV) DNA. This discovery made HPV vaccination against cervical cancer and the commercial availability of HPV testing possible. HPV vaccination has been available since 2006 and there are currently three on the market and Ian Frazer was critical in its development.
One century, four pioneers, and three vaccinations later, and cervical cancer continues to be a global public health problem and is the leading gynaecologic cancer in developing countries. Pap smear screening reduces cervical cancer incidence; however, most developing countries lack the resources to implement such programmes which require high coverage of women at risk, quality screening tests, and effective follow-up and treatment. Pap smear screening requires a doctor or nurse to collect a sample, a cytotechnician to process and interpret the sample, and a pathologist to confirm positive results. All women with abnormal results should be contacted to receive appropriate treatment.
Despite these challenges, locally, there has been a steady decrease in cervical cancer rates and in our last review the incidence was 15.7/ 100, 000. In May 2018, the World Health Organization (WHO) director general announced a global call for action to eliminate cervical cancer. This aims to achieve a global incidence of 4 per 100, 000, down from the current figure of 13.5 /100, 000, through vaccination, screening, and treatment. This initiative recommends HPV DNA detection as the primary screening test rather than inspection with acetic acid or Pap smears because of the higher sensitivity of HPV testing. Should we therefore implement HPV testing as our primary screening modality?
Evidence suggests that there is a 50 per cent reduction in cervical cancer deaths and late-stage disease from a single lifetime HPV test. The improved sensitivity of HPV testing is advantageous on a public health level as it facilitates less frequent testing without compromising efficacy and makes the WHO recommendation of at least two tests in a 10-year interval between ages 35 and 45 possible. Because of the lower sensitivity of the Pap smear, more frequent tests are needed. HPV test results are automated and not prone to human interpretation while Pap smears require cytologists which may contribute to longer wait times for reports in the public setting. Some HPV test results may be ready within one to three hours. Self-test kits allow testing at home and urine HPV tests do not require a pelvic examination. HPV testing is also useful in guiding the management of abnormal Pap smears. The major limitation of HPV testing is the cost locally. Also, widespread HPV testing may increase the referrals for colposcopy unless triage measures such as Pap smear or visual inspection with acetic acid are implemented.
The WHO has advised that countries with effective Pap smear screening continue doing so until national HPV testing can be implemented. Fifty per cent of women who develop cervical cancer have never had a Pap smear and an additional ten per cent have not had one done in five years prior to diagnosis. Therefore, sixty per cent have not been adequately screened. For Jamaica, this means we need expedite the implementation of a national Pap smear screening programme, reminding women that doing frequent smears improves the accuracy of the test. Many advances have been made since the discoveries of Babeş and Papanicolaou; however, the importance of their discoveries remain relevant today.
Dr Natalie Medley is a consultant obstetrician and gynaecologist and gynaecologic oncologist at the Mona Institute of Medical Sciences, University Hospital of the West Indies. She can be contacted at (876) 977-1512, (876) 618- 6048 or nmedsingh@gmail.com.
