Q&A: What is the difference between a Covid PCR test and a LAMP test for coronavirus?

Testing for coronavirus is on everyone's mind right now. But what's the difference between the two most readily available tests?

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Several countries are insisting that travellers produce a negative Covid-19 test certificate to enter. From November 23rd Spain too is joining the list. The prerequisite for entry is a PCR test taken in the 72 hours before arrival.

So, what is the difference between a PCR and a LAMP test?

What is a Covid-19 PCR test?

PCR (polymerase chain reaction) test, is the most common form of testing in the UK and is seen as fairly reliable. A swab is taken from the back of the throat or the very top of the nostrils. Both are highly uncomfortable. The sample is sent to a laboratory to detect genetic material in the virus called RNA (the nucleic acid that converts DNA into proteins). RNA is collected as it carries the genetic information of coronavirus.

It is a time-consuming process involving a solution (aka reagent) which is added to the sample and then processed through various temperature steps in a thermal cycler so that it multiplies into larger quantities of DNA. Bioscientists can then see whether the SARS-CoV-2 virus (the virus that causes COVID-19) is present.

It takes around 12 hours which is why results take so long to be issued.

PCR tests have been used throughout the coronavirus pandemic by the Channel Island of Jersey, which has been providing them free for arrivals.

What is a LAMP test for coronavirus?

“LAMP” (loop-mediated isothermal amplification) tests uses a swab to collect material from the throat and nose but this is not processed in a thermal cycler. It produces many more viral RNA copies without the need to heat and cool – a constant temperature is used. The samples are then placed in vials of reagents (substances that produce a chemical reaction to detect the RNA), then heated in a special machine for 20 minutes. The sample is analysed to confirm the presence or not of SARS-CoV-2 RNA.

A LAMP test can be processed within a couple of hours. What’s more, it can be carried out on site. This method is currently being used at Heathrow Airport in conjunction with Swissport and Collinson for its testing centres in Terminal 2 and Terminal 5.

There are worries that this method is not as accurate as a PCR test and false positives and false negatives can happen. Some say a second LAMP test should be taken to ensure accuracy. Many countries are worried about false negatives and that is way PCR test are the preferred test.

Can I get a test through the NHS?

You cannot get a free test through the NHS if it is for travel. This service is for those concerned that they may have contracted coronavirus and have symptoms. 

So a test for travel purposes must be acquired privately. Many countries insist on a certificate produced by a lab approved by Ukas, the UK’s national accreditation body. Search online for a Covid-19 Walk-through testing site near you.