Cervical cancer screening involves a doctor or nurse taking a small sample of cells from the surface of the woman's cervix.
There are two main ways of screening for cervical cancer: 1. Liquid based cytology. 2. A Pap (Papanicolaou) smear (cervical smear).
Liquid based cytology - this is done using a speculum, which is placed inside the vagina and scraping the cervix with a small brush. The head of the brush which has cervical cells is broken off, it is placed in a small pot of liquid and sent to the lab. Experts say the cells are better preserved with liquid based cytology (LBC) compared to the Pap test, which places the cells directly onto a microscope slide.
The cells are carefully examined in the lab and any abnormal ones are reported.
The PAP smear - the doctor or nurse starts by inserting a speculum into the patient's vagina, spreading it open so that access to the cervix is possible. The health care professional then scrapes the outer opening of the cervix with an Aylesbury spatula, and collects a sample of cells.
These cells are placed directly onto a microscope slide and sent to the lab where they are carefully examined and abnormal ones reported.
In the United Kingdom, screening programs changed to liquid-based cytology in 2008.
What is the cervix?The cervix uteri (Latin for "neck of the womb") is the narrow portion of the lower part of the uterus, where it joins the top end of the vagina. The cervix is conical or cylindrical in shape and protrudes through the upper anterior vaginal wall. With appropriate medical equipment, half the cervix's length is visible.
Liquid based cytology versus the PAP smear testAn article in The Lancet in explained that liquid based cytology (LBC) is no better than the conventional (Pap) smear test, which has been used for over three decades. Experts have said that LBC is more effective because it is more sensitive, the cells are better preserved before they get to the lab for analysis, meaning there are fewer cases of unsatisfactory samples for assessment.
However, after reviewing 56 studies, involving 1.25 million samples, the authors concluded that there is no evidence demonstrating LBC's superiority over conventional smear tests. The authors added "Although we did not find liquid-based cytology to be more accurate than conventional cytology, equivalent performance might be sufficient if liquid-based cytology has other advantages, such as the opportunity for concurrent HPV DNA testing, reduces reading times, or is more economical than conventional cytology."
Who should undergo cervical screening, and how often?Cervical screening in the USA
The United States Preventative Services Task Force (USPSTF) published its new guidelines in March 2012 in Annals of Internal Medicine. It recommended that females aged from 21 to 65 years should have a Pap smear every 3 years. A woman aged from 30 to 65 years who also undergoes an HPV (humanpapillomavirus) simultaneously could extend the screening intervals to once every five years. Females younger than 21 should not be screened, regardless of sexual history. The guideline authors explained that screening younger females makes no difference to cervical cancer incidence and/or mortality.
Women over the age of 65 who have undergone adequate prior screening and are not otherwise at risk require no further screening.
The American College of Obstetricians and Gynecologists, in October 2012 recommended that the Pap test and the HPV test should be done together. However, they suggest that only females aged 30 years or more should undergo screening, and it should occur once every five years.
A high percentage of women who have had a total hysterectomy still have Pap tests in the USA; a pointless screening.
Cervical cancer screening UK
The National Health Service cervical screening program contacts women aged from 25 to 60 every 3 to 5 years and invites them to have a cervical screening test. The exact age varies according to the different countries in the UK. In England and Northern Ireland females between 25 and 64 are screened, in Scotland from 20 to 60, and in Wales from 20 to 64.
UK health authorities say that the screening interval varies according to a woman's age. It is possible to pick up most cancers by screening women aged 25-49 years every 3 years, and every 5 years if they are aged between 50 and 64.
Checking 25-49 year-old women every three years prevents 84% of cervical cancers from developing, while screening every 5 years for the same age group only prevents 73%.
What do the lab test results mean?Cervical screening tests results can vary enormously and may often reflect problems with the test rather than the presence of any abnormal cells. Sometimes the patient may be asked to repeat the test because the sample was "inadequate" (it could not be read properly).
Inadequate samples could be due to:
- The sample had too few cells
- The patient had an infection. In such cases the cells could not be seen clearly enough
- The patient was menstruating and there was too much blood to see the cells properly
- There was an inflammation in the cervix, making it hard to see the cells clearly enough
What is a "borderline" result? - this means that the pathologist detected cell changes, but they are most likely nothing to worry about because they are very near normal and will probably resolve on their own. The patient will probably be asked to undergo another test within six months.
What is cervical erosion? - sometimes referred to as an ectropion. This means the glandular cells can be seen on the surface of the cervix. Erosions are common and nothing to worry about - they are common among women on the contraceptive pill, teenagers and pregnant mothers. There may be some slight bleeding after sex. In the vast majority of cases, cervical erosions resolve without treatment.
Abnormal lab test resultsAn abnormal result means that the pathologist detected changes in the patient's cervix. This does not necessarily mean that the woman has cervical cancer - in fact, in most cases she does not.
Most likely, the abnormal changes in the cervical cells are caused by HPV. The changes may be low-grade (minor) or high-grade (serious). As mentioned earlier, in the majority of cases, minor changes resolve without treatment.
More serious changes can eventually become cancerous if they are not removed. They are usually called "pre-cancer". It is vital that the patient does not let these changes get worse.
On rare occasions, an abnormal test result may show that the patient has cancer. Further tests will be required to confirm this. Cervical cancer is easier to treat if it is diagnosed early on.
In the UK, abnormal test results may say:
- Mild dyskaryosis - mild or slight cell changes
- Moderate dyskaryosis - moderate cell changes
- Severe dyskaryosis - severe cell changes
- CIN 1 (mild cell changes) - this means one third of the thickness of the skin that covers the cervix has abnormal cells.
- CIN 2 (moderate cell changes) - two-thirds of the thickness of the skin that covers the cervix has abnormal cells.
- CIN 3 (severe cell changes) - all the thickness of the skin that covers the cervix has abnormal cells.
According to the CDC (Centers for Disease Control and Prevention), more than 3 million women get abnormal or unclear PAP test results, of which only about 10,000 have cervical cancer.
Written by Christian Nordqvist