Cervical screening (smear test)
Also known as: smear test, Pap test, Pap smear, HPV test, cervical cytology
A sample of cells brushed from the transformation zone of the cervix, the band where the columnar lining of the cervical canal has been replaced by squamous cells and where nearly all cervical cell changes begin, taken with a small soft brush passed through a speculum. In England the sample is tested first for high-risk human papillomavirus (HPV), the virus behind almost all cervical cancer, and the cells are examined under the microscope only if that virus is found. Screening looks for the risk of cancer developing rather than for cancer itself, and it is offered to everyone with a cervix, including trans men and non-binary people.
- Kind
- Pathology or cytology test
- Categories
- Pathology & cytology, Infectious disease & microbiology, Screening & clinical assessment
- Specimen
- Cytology sample
- Method
- Nucleic acid amplification test, Cytology
What it measures
| Measure | What it tells you |
|---|---|
| High-risk HPV | The virus types that cause cervical cancer, chiefly types 16 and 18. A negative result means the chance of cancer developing before the next screen is very low. |
| Cytology (cell changes) | Looked at only when high-risk HPV is found. Cells are reported as normal, borderline, or as low-grade or high-grade dyskaryosis, according to how abnormal they appear. |
| Sample adequacy | A sample with too few cells, or obscured by blood or inflammation, is reported as inadequate and has to be repeated. |
Why it is ordered
- Routine screening for everyone with a cervix aged 25 to 64 in England, at intervals that depend on age, the previous result and the programme (the four UK nations differ)
- A repeat a year after a high-risk HPV result with normal cells, to see whether the infection has cleared
- Follow-up after treatment of cervical intraepithelial neoplasia (CIN), as a test of cure
- Trans men and non-binary people who have a cervix: those registered with a GP as male are not sent automatic invitations and need to ask for screening
- Not for investigating symptoms: bleeding between periods, after sex or after the menopause needs an examination of the cervix and referral, not a screening test
How it is done
A speculum is passed into the vagina so that the cervix can be seen, and a small soft brush is rotated in the opening of the cervix for a few seconds. The tip of the brush is put into a pot of preservative liquid and sent to the laboratory (liquid-based cytology). The appointment takes a few minutes and is usually done by a practice nurse.
Preparation. None is needed, although it is better not to book during a period because blood makes the sample harder to read, and vaginal medicines, lubricants and spermicides are avoided for a couple of days beforehand. A test that falls due in pregnancy is usually put off, and screening is normally taken up again about twelve weeks after giving birth; anyone who is pregnant and has been invited should say so when booking. Discomfort and anxiety can be reduced by asking for a smaller speculum, a different position or a longer appointment, and a course of vaginal oestrogen is sometimes prescribed first when the tissues are thin after the menopause or on testosterone.
Reading the result
| Finding | Usual meaning |
|---|---|
| No high-risk HPV found | Routine recall; the chance of cervical cancer developing before the next invitation is very low |
| High-risk HPV found, cells normal | Screening is repeated in a year, because most infections clear on their own |
| High-risk HPV found with abnormal cells | Referral for colposcopy: the cervix is examined under magnification and a biopsy or loop excision may be taken |
| High-risk HPV still present on repeat testing | Screening is repeated after a further year; high-risk HPV that is still present at that second repeat leads to colposcopy even when the cells look normal, because it is persistent infection that leads to cancer |
| Inadequate sample | Repeated after about three months; repeated inadequate samples lead to colposcopy |
Reference ranges vary by laboratory, method, age, sex and clinical context; a result is read against the person, not a table.
Limitations
Screening lowers the risk of cervical cancer a great deal but does not remove it. HPV vaccination protects against the commonest high-risk types but not all of them, so screening invitations still apply to people who have been vaccinated. A sample can miss an abnormal area, and adenocarcinoma arising high in the cervical canal is harder to detect than squamous disease. A positive HPV result is common, says nothing about when or from whom the virus was acquired, and in most people clears without treatment within about two years. The test says nothing about the ovaries, the lining of the uterus or other infections, and it cannot be used to investigate bleeding or pain, which need an examination. Kits for taking a sample at home are being introduced in some programmes for people who do not attend.
Catalogued concepts this page covers
Concepts of the master test taxonomy that resolve to this page; each links to its category.