Both nasopharyngeal aspirate (NPA) tests and swab tests can be used to test for various respiratory (breathing) viruses, including coronavirus (COVID-19). Testing collects a sample of mucus from the back of the throat that can then be tested in our laboratories to identify the particular virus causing the infection. This information from Great Ormond Street Hospital (GOSH) explains when these tests will be used and what to expect when you or your child has one.
Respiratory illness can be caused by a virus, a bug that is often coughed or sneezed out into the air in droplets that fall to the ground or onto surfaces quite quickly. It can cause symptoms including a runny nose, sore throat, cough and noisy breathing. The best way of identifying the virus causing the symptoms is by looking at a sample of mucus. Mucus is the coating that lubricates the inside of the nose and traps things such as dust as well as bugs.
Who is being tested?
At the moment, during the coronavirus pandemic, we are carrying out more nasopharyngeal aspirate (NPA) and swab tests than usual at GOSH.
We are currently testing all children and young people admitted to GOSH for an overnight stay or longer and those having certain procedures, such as those involving anaesthetic, whether or not they are showing symptoms of coronavirus. The parent or carer accompanying them may also need to be tested. Parents and carers who are showing symptoms should not come to GOSH.
This is in line with national guidance – if this guidance changes, we will update this information.
What does the test involve?
A doctor or nurse will collect the mucus sample. They will be wearing gloves, an apron, a mask and a visor – this is to keep everyone safe. There are two ways we collect a sample of mucus.
Nasopharyngeal aspirate test
The doctor or nurse will collect the mucus sample using a catheter (a thin, plastic tube) attached to a suction machine. This sucks out a sample of mucus and collects it in a specimen pot.
First, they connect a fresh catheter to a suction machine and check the settings. One end of the catheter is sealed in a specimen pot. Another catheter comes out the lid of the specimen pot. This means that the mucus can be collected safely without it getting spilt.
The doctor or nurse will gently insert the catheter into one nostril and pass it through the nose to the top of the throat at the back – this area is called the nasopharynx. The suction machine will suck up a sample of mucus into the specimen pot – our laboratory does not need much. The doctor or nurse will gently pull the catheter out, back through the nostril and the test is complete.
It's worth noting that the NPA is being offered to patients, and is the only test suitable for under-twos.
Parents and carers will be offered the swab test. Swab tests can also be given to patients if they are over the age of two and prefer it.
The doctor or nurse will collect mucus samples using two swabs, which are like long cotton buds.
First, they will rub the first swab against the inside of your nose to collect the first sample. They have to take the sample from the top of your nose so this may be a bit uncomfortable. They will then ask you to hold your mouth open, so they can rub a second swab against the back of your throat to collect the second sample – our laboratory does not need much.
Immediately after each sample is taken, the swabs are put into their sterile containers. This is so that the mucus can be stored and transported safely without it getting spilt. The test is now complete.
One of our porters will take the specimen pot or swab containers to our laboratory, where a scientist will test it for the virus.
Are there any risks?
Collecting a sample of mucus can release virus particles into the air, which is why our staff wear full protective gear – gloves, apron, mask and visor – to protect themselves. The specimen pot is ‘closed’ once collected, so there is no chance of virus (if it is present) escaping.
Having a nasopharyngeal aspirate or swab test may tickle, but is unlikely to hurt. It can make you sneeze or cough a bit, but this will only last a few seconds.
Getting the results
Scientists in our laboratory will carry out the tests to see whether the virus is present or not as quickly as they can. This usually takes 48 hours.
When they have the results, they will add it to your child’s health record, so that your doctor can talk to you about it. They will tell you whether your child has the virus and what it might mean for any planned treatment.
If you are staying with your child and the test shows that you have the virus, even if you are not showing any symptoms, we will ask you to go home and stay in self-isolation for 7 days. If possible, another parent or carer should take over from you and stay with your child at GOSH instead.
If you or your child test positive for COVID-19, we will still ensure your child gets the care and treatment they need. If you have any concerns about having the test, please speak to your clinical team
Further information and support
Talk to your doctor or nurse if you have any questions about the test or what the test results mean for you and your child.