Cervical cancer screening is a medical screening test designed to identify risk of cervical cancer. Cervical screening may involve looking for viral DNA, and/or identifying abnormal, potentially precancerous cells within the cervix as well as cells that have progressed to early stages of cervical cancer. One goal of cervical screening is to allow for intervention and treatment so abnormal lesions can be removed before progression to cancer. An additional goal is to decrease mortality from cervical cancer by identifying cancerous lesions in their early stages and providing treatment before progression to more invasive disease.
Currently available screening tests fall into three categories: molecular, cytologic, and visual inspection. Molecular screening tests include nucleic acid amplification tests (NAAT), which identify high-risk human papillomavirus (HPV) strains. Cytologic tests include conventional Pap smear and liquid-based cytology. Visual Inspection tests involve application of a solution to enhance identification of abnormal areas and can utilize the naked eye or a colposcope/magnifying camera.
Medical organizations of different countries have unique guidelines and screening recommendations. The World Health Organization has also published guidelines to increase screening and improve outcomes for all women, taking into consideration differences in resource availability of regions. Management of abnormal screening results can include surveillance, biopsy, or removal of the suspicious region via surgical intervention. Diagnosis of more advanced cancer stages may require other treatment options such as chemotherapy or radiation.
General screening procedure
The procedures for testing women using Pap smear, liquid-based cytology, or HPV testing are similar. A sample of cells is collected from the cervix using a spatula or small brush. The cells are then checked for any abnormalities.
To take a sample of cells, the healthcare clinician inserts an instrument, called a speculum, inside the vagina. The speculum has two arms that spread the walls of the vagina apart to see the cervix. Then, they scrape the surface of the cervix with a spatula or small brush. This collects a sample of cells from the outer layer of the cervix.
Self-collection is also an option when testing by a provider is unavailable or uncomfortable for a patient. When utilizing HPV testing, self-collection is as accurate as swabbing by a provider. This equality has not been demonstrated for other testing, such as pap smear or liquid-based cytology.
With a Pap smear, cells collected using a spatula are smeared onto a slide for examination under a microscope. In liquid-based cytology, a sample of cells is taken using a small brush. The cells are put into a container of liquid and analysed for abnormalities. Cervical cells to be tested for HPV are collected similarly.
Types of screening
Molecular Molecular testing identifies an infection called human papillomavirus, or HPV. Human papillomavirus (HPV) infection is a cause of nearly all cases of cervical cancer. Most women will successfully clear HPV infections within 18 months. Those that have a prolonged infection with a high-risk type (e.g. types 16, 18, 31, 45) are more likely to develop Cervical Intraepithelial Neoplasia, due to the effects that HPV has on DNA.
The screening process utilizes nucleic acid amplification testing to look for DNA or RNA of the virus present within cervical cells. Some tests can identify up to 14 different types of high-risk strains.
Accuracy of HPV testing report: sensitivity 88% to 91% (for detecting CIN 3 or higher) to 97% (for detecting CIN2+) specificity 73% to 79% (for detecting CIN 3 or higher) to 93% (for detecting CIN2+)
Cytologic
Conventional Pap smear
In the conventional Pap smear, the collected cells are smeared on a microscope slide, and a fixative is applied. The slide is evaluated in a pathology lab to identify cellular abnormalities.
Accuracy of conventional cytology report: sensitivity: 55% to 88% specificity: 71% to 94%
Liquid-based monolayer cytology
In liquid-based monolayer cytology, the collected cells are placed into a liquid medium. The sample is evaluated in a pathology lab to evaluate cellular abnormalities.
Accuracy of liquid based monolayer cytology report: sensitivity 57% to 90% specificity 64% to 97%
Visual inspection Visual inspection involves the application of ascetic acid or Lugol's iodine solution to the cervix. These solutions highlight abnormal areas for easier identification with the naked eye. Visual inspection can include receiving a colposcopy if results from cytologic screenings produce abnormal results. A magnifying camera called a colposcope can also be utilized for clearer viewing when available. Through visual inspection, abnormalities can be detected within the cervix. If detected, abnormal tissue can then be sampled and taken for further testing.
Combination testing (co-testing) Combination testing, or co-testing, is when individuals receive both molecular high-risk HPV testing and cytology. These results can be utilized to calculate the patient's immediate risk for cervical intraepithelial neoplasia grade 3 or cancer (CIN3+).
The calculated risk can be used to recommend appropriate follow-up options.
Recommendations Cervical screening demographics are largely measured by motives or reasons for participation and thus vary between age, socio-economic status, race, location, and ethnicity. In practice, cervical screenings are often undergone to test for cervical cancer, but are dually used to test for other conditions such as STIs, inflammation, and precancerous cells.
Cervical screenings typically begin at ages 21–25, with the recommended age being 21. Testing for cervical cancer should occur at least every 3 years, and HPV every 5 years. However, if test results are abnormal, healthcare providers may suggest more frequent screenings. If patients are sexually active, recommendations for screenings may change or vary as increased sexual activity is a strong risk factor for developing HPV.
Public health screening interventions that are available for cervical cancer screening globally include: cytology-based screening, visual screening, HPV DNA testing, colposcopy, and spectroscopic techniques.
Cervical cancer has a distinct disparity in diagnosis associated with access to care, specifically access to cervical screening. This disparity is reflected in higher rates of cervical cancer found among minority groups in countries with higher economic status, as well as higher rates of cervical cancer found in lower-income global areas in comparison to advantaged groups. Globally, cervical cancer is most prominent in developing countries, with 80% of cases globally occurring within lower socio-economic countries. Within the US, there is a significant disparity in rates of cervical cancer diagnosis among black women compared to white women, with mortality rates of black women with cervical cancer being severely underestimated. In light of such disparities, appropriate screening and greater efforts towards intervention are highly recommended.
Recent studies show that using the health belief model, self-efficacy, knowledge of benefits, and knowledge of susceptibility were associated with higher cervical screening rates. These individuals tend to be college graduates, older, educated on cervical cancer, or married. On the other hand, individuals with more socioeconomic barriers are associated with lower screening uptake. A 2024 review shows that HPV and cervical cancer screening content are being disseminated on social media platforms such as Facebook and Twitter. Health communication content is being used to encourage the uptake of cervical and HPV screening, making education accessible through these platforms, which may be helpful in reaching the World Health Organization’s goal of eliminating cervical cancer through HPV screening.
Different countries and medical organizations have specific cervical screening recommendations to guide patient care.
World Health Organization In 2021, the World Health Organization published the second edition of WHO guideline for screening and treatment of cervical pre-cancer lesions for cervical cancer prevention. Within this publication, they outline 23 recommendations addressing differences in guidelines for women living with or without HIV. The quality of evidence is rated strong, moderate, low, or very low. Some of the recommendations are included below; this is not a comprehensive list. HPV molecular testing is recommended as primary screening, with or without triage, in all women. HPV screening should occur every 5 to 10 years. When used, VIA or cytologic screening should occur every 3 years. Begin screening at the age of 30 Stop screening at the age of 50, as long as the most recent two tests were negative
Europe
Most countries suggest or offer screening between the ages of 25 and 64. According to the 2015 European guidelines for cervical cancer screening, routine HPV primary screening should not begin under 30 years of age. Primary testing for oncogenic HPV can be used in a population-based program for cervical cancer screening. In England, the NHS cervical screening program is available to women aged 25 to 64; women aged 25 to 49 receive an invitation every 3 years and women aged 50 to 64 receive an invitation every 5 years to undergo HPV testing. If there is a positive HPV test result, then patients undergo further cytology (Pap smear).
United States In the US, doctors follow the guidelines of both the American College of obstetrics and Gynecology (ACOG) or the United States Preventative Services Task Force (USPSTF) for cervical cancer screening, which are primarily stratified by age. Screening is recommended for women between ages 21 and 65 every 3 years using cervical cytology, regardless of age at sexual initiation or other high-risk behaviors.
The age-based recommendations by both institutions are as follows:
No screening recommended for women less than 21. From ages 21 to 29, a pap smear is recommended every three years with cervical cytology alone. From ages 30 to 65, women can choose between a pap smear every three year or an FDA-approved primary high risk HPV test every five years, or pap smear and HPV co-testing every five years. In women over the age of 65, screening for cervical cancer may be discontinued in the absence of abnormal screening results within the prior 10 years and no history of high-grade lesions. For women with other comorbidities these guidelines may differ. In addition to the age-based guidelines provided by the USPSTF and ACOG, are risk-based guidelines established by a consensus of medical professionals (i.e., the American Academy of Family Physicians, the American Cancer Society, ACOG, etc.), government organizations (i.e., the National Cancer Institute), and patient advocacy groups. These risk-based guidelines take into account an individual's current and prior cervical screening results in order to estimate an individual's immediate and 5-year risk of developing CIN 3 or higher. The risk estimates are then used by practitioners to help determine screening and surveillance intervals, as well as management of results (i.e., further evaluation with colposcopy or treatment). Based on an individuals risk estimates, the practitioner may recommend the individual continue with age-based screening recommendations or return for surveillance at shorter intervals (i.e., 1 year or 4 months). Alternatively, an individual's risk estimate may warrant the recommendation of colposcopy with biopsy for further evaluation or expedited treatment.
United Kingdom