What does ‘C’ and ‘T’ mean on a Covid test? How to read results of a lateral flow test at home

Lateral flow testing is a fast and simple way to test people who do not have symptoms of Covid, but who may still be spreading the virus

Many people across the UK will now be used to taking lateral flow tests at home for Covid-19.

But what does ‘C’ and ‘T’ mean on the test and how should results be read?

Sign up to our NationalWorld Today newsletter

The i newsletter cut through the noise

Here’s everything you need to know.

What are lateral flow tests?

Lateral flow testing is a fast and simple way to test people who do not have symptoms of Covid, but who may still be spreading the virus.

The tests are easy to use and give a quick result, but those who test positive must immediately self-isolate to avoid passing the virus on to others.

They work by detecting proteins (antigens) that are present when a person has Covid.

The test kit is a hand-held device with an absorbent pad at one end and a reading window at the other.

Inside the device is a strip of test paper that changes colour in the presence of antigens.

How do I take a lateral flow test?

Taking a lateral flow test usually involves taking a sample from the back of the throat near the tonsils and the nose, or just from the nose only, using a swab.

The swab is then dipped into an extraction solution which is dripped onto the device’s paper pad.

The tests give a quick result, as the sample does not need to be sent to a lab.

What does ‘C’ and ‘T’ mean on a Covid lateral flow test?

If you have taken a lateral flow test for Covid before you will have noticed it includes letters.

The ‘S’ is where the sample goes and in the separate section above this you will have noticed a ‘C’ and a ‘T’.

If there is one line next to the C then this means the test is negative

If there are no lines at all or just one line next to the T, then this means the test is void and you will need to retake with a fresh test kit.

However, if there are two lines, one being next to C and one next to T, even if they are faint, then this means the test is positive. You or your test provider must then report this test result to the NHS.

How effective are lateral flow tests?

The Department of Health and Social Care (DHSC) explains that lateral flow tests can help to drive down the spread of Covid and “can find positive cases with high levels of virus that are easy to transmit to others, helping to intercept and reduce further infections”.

Lateral flow tests used by the UK government go through a rigorous evaluation by the country’s leading scientists, says the DHSC.

This means they are accurate, reliable and successfully identify those with Covid who don’t show symptoms and could spread the virus without realising.