Sometimes test results are inaccurate. We call these results false positives and false negatives.
False positives and false negatives are unavoidable. They happen in every screening programme.
But our change to how we do cervical screening in 2020 will mean fewer false negatives than before.
Benefits and limitations of cervical screening
False positive results
Your result may be positive even though there is no HPV infection or changes to cells of the cervix. This is called a false positive.
A false positive may mean you will have further tests and find there was no risk of cancer at that time.
False negative results
Your result may be negative even though there is a HPV infection or abnormal cells in the cervix. This is called a false negative.
A false negative may mean that you are not sent for further tests. This could be a missed chance to stop cancer developing.
How abnormalities can be missed
We will check your screening sample for HPV first.
If we do not find HPV, we do not need to check for abnormal (pre-cancerous) cells. This is because your risk of developing cervical cancer is very low if you do not have HPV.
But in some cases people who have a negative HPV test result go on to develop cancer.
A negative HPV test does not mean you won't get the HPV infection in the future.
How abnormal cells can be missed
If we find HPV in your sample, we will check the sample for any abnormal cells. But sometimes abnormal cells can be missed.
This can happen because:
- sometimes abnormal cells do not look much different to normal cells
- there may be very few abnormal cells in the sample
- the person reading your sample may miss the abnormality (this happens occasionally, no matter how experienced the reader is)
Things you can do
No test in any screening programme finds all abnormal cervical cells.
Because of the limitations of cervical screening, it's important that you:
- pay attention to possible symptoms of cervical cancer
- book and go to your screening test when it is due
Non-urgent advice: Contact your GP immediately if:
- you have concerns or symptoms
Even if you have had a recent normal screening result, never ignore symptoms.