Cervical screening

Human papilloma virus (HPV) and cervical cancer¹²³

99.8% of cervical cancers are caused by high-risk strains of human papilloma virus (HPV).

Without vaccination, around 50-79% of sexually active women have a lifetime risk of being infected with human papillomavirus (HPV) and almost 40% of women are infected with HPV within two years of first sexual activity. A paper by Public Health England showed that the prevalence of high-risk strains of HPV in sexually active women aged 16 - 18 had dropped from 15% in 2008, prior to vaccination, to 2% in 2018.

Most HPV infections are transient; abnormal cells often resolve untreated when the virus clears. If HPV persists, abnormal cells can, if left untreated, turn into cancer over time.

The World Health Organization have called for a global call for action to eliminate cervical cancer (defined as an incidence rate which has reduced to below 4 per 100,000 women). To accomplish this, they have set targets of 90% of girls being fully vaccinated against HPV by the age of 15, 70% of women screened by 35 and again by 45, and 90% of women treated for their pre-cancerous changes or invasive cancer. The aim is for every country to meet the 90:70:90 target by 2030.

Cervical cancer epidemiology⁴

Cervical cancer is the third or fourth most common female malignancy worldwide. It occurs much more frequently in low- and middle-income countries.

2017 - 19 figures show that:

• In females in the UK, cervical cancer is the 14th most common cancer.

• It is the 19th most common cause of cancer death and accounts for around 2% of new cancers in women.

• It has been estimated that the UK lifetime risk of developing cervical cancer is 1 in 142.

Incidence is dropping due to HPV vaccination and so current figures may be lower.

Screening versus the investigation of symptoms

Cervical screening is a test for asymptomatic women. Women who have symptoms that may suggest cervical cancer (such as abnormal bleeding) need a full clinical assessment and examination, with appropriate referral not to be delayed by waiting for a cervical screening result. Women who ask for a screening test outside of the usual interval (below 25, or before it is due) may be doing so because they have symptoms - we should proactively ask about symptoms in this situation, and assess appropriately if they are present.

Benefits of cervical screening ⁵

It has been estimated that regular cervical screening can prevent around 70% of cervical cancers from developing.

Coverage of the programme⁶

Cervical screening is available in all countries of the UK to those of the female sex (regardless of gender identity) who have not had their cervix removed and are aged 25-64. Frequency of screening varies by country of the UK - details are in the further reading section. The first invitation is sent at the age of 24.5 years. Screening is not recommended below the age of 25, as cell changes in the cervix at that age will often reverse spontaneously, so there is a risk of over-treatment, which can have consequences in a later pregnancy. ⁷

All eligible people who are registered with a GP as female automatically receive an invitation by mail. Trans men (who are of the female sex but have changed the gender marker on their notes to male) do not receive invitations if registered as male with their GP, but are still entitled to screening if they have a cervix. Practices should have their own system to make sure that this cohort are recalled. The RCGP has for some years called for computer notes to have separate sex and gender markers, to reduce the risk of this group being missed, but this has not yet happened.⁸

Women with HIV should have colposcopy at diagnosis and then annual cervical screening until the age of 64; annual tests should continue even if they remain negative. This is because this cohort has an increased risk of cervical cancer and of high-risk strains of HPV. If screening request forms are marked to indicate that the patient has HIV then most laboratories will recall annually; if this does not happen automatically, practices will have to keep their own records and recall women with HIV each year. ⁹

The screening process⁶

A speculum made from disposable plastic (or from metal, which should be warmed) should be inserted vaginally to view the squamocolumnar junction of the cervix. A brush is used, which is rotated against the squamocolumnar junction (usually in the cervical canal). Two different types of brush are available; those who take cervical screening samples should ensure that they are up to date with the brush and technique used in their area.

Management of results⁵¹⁰

The cervical screening programme in the UK now uses primary HPV triage - samples are tested for HPV and if negative, the sample is discarded, the result given as negative and the woman recalled at the usual interval. If the HPV test is positive, cytology is carried out, and if dyskaryosis is seen on cytology then the woman is referred for colposcopy. A woman with a positive HPV test but negative cytology will have a repeat screen in one year, and if this happens three times then she will be referred for colposcopy, despite negative cytology.

If the high-risk HPV test result is unavailable or cytology is inadequate at any screening episode, a sample is repeated in no less than three months. After two such results, a referral to colposcopy is done. All referrals to colposcopy which result from cervical screening are done by the screening programme; the GP will be informed, but will not be expected to do the referral.

Interpreting cytology results

If the test for HPV is positive, the cells are analysed to look for abnormalities in the appearance of the nucleus and other aspects of cell morphology (dyskaryosis):

• Inadequate - this may be because the cervical sample:

  • Was taken but the cervix was not fully visualised.

  • Was taken in an inappropriate manner (for example, using an unapproved device).

  • Contains insufficient cells.

  • Contains an obscuring element (for example, lubricant, inflammation or blood).

  • Is incorrectly labelled.

• Negative - no abnormality is detected.

• Abnormal - the cervical samples may show:

  • Borderline changes in squamous or endocervical cells. Cells are seen with abnormal nuclei, but the pathologist cannot say for certain that they are indicative of dyskaryosis. Many patients revert to normal smears eventually. Very few of these patients go on to develop cancer.

  • Dyskaryosis (pre-cancerous changes in the cells) - this may be mild, moderate or severe. Dyskaryosis is a cytological diagnosis - women will then progress to colposcopy, where they may get a histological diagnosis of CIN 1, 2 or 3, judged on what percentage of the cells are affected.

  • Invasive squamous cell carcinoma.

  • Glandular neoplasia. Occasionally, abnormalities of glandular cells are seen, suggestive of adenocarcinoma in situ, adenocarcinoma of the cervix, endometrial adenocarcinoma or adenocarcinoma of an organ outside the uterus.

HPV self-swabs¹¹¹²

Trials of HPV self-swabs have looked at whether this could reduce the number of women who need a speculum examination for their screening test. Women whose HPV swab was negative would not need a full sample of cells to be taken. This would reduce costs, and may encourage some of those who do not currently come for screening to attend. It could be particularly useful for those who may find speculum examinations traumatic, including some victims of sexual abuse and trans men. It may also reduce health inequalities, as cervical screening uptake is generally inversely related to affluence, and is lower in some ethnic minorities. As of 2024, universal use of self-swabs has not yet become a feature of the UK screening programme, but it is used to try and target non-attenders in some areas.