Choices…Choices….

Location Medical Services (UKAS REG No. 22418) provides 2 covid test options.. (not including blood antibody tests – but as these are of limited value, they are mentioned only briefly at the end of the page for completeness).

COVID-19 PCR Tests (Lab Analyzed - Results reported 24-48 hours later)

Covid Rapid tests (On site - Results in 15-30 min)

 To help you make the right choice we have provided some detailed information on both test options below – It's important to understand which is right for you - but if you are really short of time a very brief summary would be:

PCR testing remains the “Gold Standard” against which every new test is measured. However, it is lab based – meaning results cannot normally be obtained “same day” and the need to process these tests in labs makes them a more expensive option.

PCR tests are the requirement for most airlines & immigration authorities.

Rapid Testing has only just gained “official” validation from Public Health England as part of the UK’s mass testing programme. The main advantage is that results are available inside 30 minutes – meaning any infectious people can be identified and isolated immediately. Unfortunately, rapid tests are not quite as accurate as PCR testing. Undoubtedly “better than nothing” in terms of allowing mass testing to take place – but it’s important to read beyond “rapid” and “cheaper” and understand what the lower accuracy actually means in terms of risk and potential disruption.

Rapid tests are not accepted by most airlines or immigration authorities for the purposes of international travel.

PCR Testing – General Background

Polymerase chain reaction (PCR) testing is currently the most common form of testing in the UK and is seen as highly reliable when combined with proper swabbing technique.

For PCR tests, a nasal swab is used to collect an RNA sample (the nucleic acid that converts DNA into proteins) from the patient's tonsils and inside their nose.

RNA is collected as it carries the genetic information of this specific virus.

This is then sent to a laboratory where the sample is heated and cooled so it multiplies into larger quantities of DNA. This is a complicated process that takes time and requires lab-based equipment that cannot be moved around easily – hence all samples must travel to a lab for analysis.

In the lab technicians can then see whether the SARS-CoV-2 virus (the virus that causes COVID-19) is present and, if necessary, should be able to re-sequence the tests to differentiate Covid-19 from other, very similar, SARS infections (there are 7 that effect humans, 4 are similar to common colds). A good lab will always do this. A poor or “under pressure” lab may report the first “hit” as covid-19 and not retest to eliminate other coronaviruses – meaning unnecessary isolation.

While PRC tests are still considered the “gold standard” for accurately detecting the presence of any coronavirus it’s important to understand that the weak link in the process is often the sample taking itself. Proper samples need to be taken from the back of the nasopharynx. This requires medical staff to administer the tests and is a mildly uncomfortable process.

At LMS we are sticklers for doing this properly but anecdotally - we often hear patients “complaining” that other tests they have had have been really “gentle” or have just rubbed the swab around the nostril – much nicer and much easier to do for a busy “swabber” but a waste of a lot of money for whoever was paying for it! Poor swabbing techniques brings the reliability of the tests down to 70% or less in terms of catching new infection in patients.

In the same way, home tests are particularly difficult to perform correctly when people are asked to “swab” themselves – not a terrible thing when they are being used by symptomatic patients who may have a progressed infection (and therefore lots of Covid RNA in their noses) but not great for detecting the newly infected carriers who will have lower levels of RNA to swab which will mainly be hiding in the back of the throat and nasal cavity.

PRC tests can also, occasionally, pick up the presence of “inactive” Covid RNA in a person who has had Covid-19 – even after the levels have dropped below infectious levels. So, caution is required in testing people recently recovered from Covid.

Why Choose PCR Testing from Location Medical?

Location Medical Services PCR tests are carried out by trained staff and all samples are transported to an approved lab – with ISO accreditation, and working with UKAS approved processes that are extensively in use at a major London teaching hospital.

Location Medical Services provides on-site testing services (for whole crews or individuals, if required) and we have the unique advantage of having a permanent “walk in” test centre in Shepperton Studios and (From 1st Dec) a “drive through” test centre near Heathrow Airport operating 7 days a week. We courier all our samples directly to the lab every day and this is included in the costs.

We have negotiated good testing capacity with our labs and maintained services through all the recent swab and reagent shortages that impacted many services. We can offer attractive discounts for clients requiring numbers of staff to be tested at prebooked dates throughout a production – as well as last minute walk in or urgent on-site tests.

Rapid Testing – Important Background Info

“Rapid Covid Tests” have been around throughout the pandemic – but were all generally considered too unreliable for any credible diagnostic use. They were being confined largely to internet-based distributors with no “pre covid” presence selling imported tests with wildly unsubstantiated or completely misleading scientific validation.

Obviously, the advantages of reliable tests giving fast results (without the need for off-site laboratory processing) are significant and, in the background, hundreds of these tests were being evaluated by the Défense Science and Technology Laboratory at Porton Down on behalf of Public Health England (PHE) as a clear indication of the variation between all the (very similar looking) tests, only 3 tests passed all 3 initial phases of testing – allowing them to be deemed suitable for full scale clinical trials and, as we understand, only one of these tests has been selected to form the mainstay of the UK government’s “Operation Moon-shot” mass testing programme. These particular rapid tests are already in use at large scale NHS testing sites across the UK as well as being rolled out as part of NHS front line staff screening processes.

Although there are a number of “rapid test” types, the predominant tests in use seem to be the lateral flow antigen test. In very basic terms an antigen is a protein that the body produces when it identifies an infection. The lateral flow tests look like pregnancy tests and work in a similar way – they are impregnated with an indicator that changes colour if it meets the antigen as it “flows” across a membrane. The presence of the antigen is an indicator of infection.

Although, in theory, the tests can work with saliva – PHE has not approved any saliva only use, so it does still require a nasal swab which, in turn, must be prepared in a dilutant (obviously in a clinically safe environment) which gives a sample that can be applied to the test. Results can be read after 15 - 30 minutes. This is obviously easier than a lab test but not quite the straightforward process some imagine. They do require a clean area protected from contamination and extreme temperatures to undertake the testing and need space to employ a robust “system” to log and monitor numbers of tests as they “resolve” without any risk of them being muddled up or disturbed.

All tests of this kind are currently restricted to administration by health care professionals only – meaning they cannot be sold for home use or postal use and cannot be “self-administered” or used by non-medical staff. Regardless of what marketing material may imply, this is the case for all rapid tests. This may change and, if so, we will update our information accordingly.

Although rapid test marketing seems to make all kinds of wild claims in terms of accuracy, test accuracy is normally measured in terms of sensitivity and specificity (or, in more general terms – does the test detect the disease it's supposed to, and does it identify people that don’t have it- both important but quite different). Many distributors’ “evidence” is based on small sample sizes and often research based generally on symptomatic populations. In fact, if you read the information provided for most rapid tests by the manufacturers, it often states quite clearly that they are 1) not for providing a definitive clinical diagnosis and 2) that they are for use on symptomatic people. The other problem with a lot of manufacturers “reliability” data is that it is not “peer reviewed” – i.e., no one has formally checked and verified it or assessed the scientific rigour with which it was conducted.

Thankfully the testing programme and large scale use by PHE is proving that some of these tests are good enough to be useful as part a covid testing programme. There is an increasing body of completely independent data showing that the few tests that make it through to deployment demonstrate reasonable levels of sensitivity and specificity and, more importantly, that they can be used in asymptomatic populations to identify people infected with covid 19 even when they have no symptoms and are totally unaware that they are carrying the virus. The all-important “asymptomatic carriers” have proven to be one of the reasons why this Coronavirus has been so difficult to control.

IN terms of data, the manufacturers figure for the tests Location Medical Services is using are:

Relative Sensitivity: 72/75 96.00% (88.75%～99.17%)

Relative Specificity: 220/220 100.00% (98.34%～100.00%)

Accuracy: 292/295 98.98% (97.06%～99.79%)

These figures are backed up by the Porton Down trials and additional published, peer reviewed research (which we are happy to share on request). We also feel it is safe to assume that, since the UK government is investing so heavily in this one test, that its use is being supported by the growing data from current NHS Covid Screening programmes across the UK.

The “Trade-Off”….

All too good to be true? Well - the sensitivity and specificity for Rapid tests are good – but they are not the 100% that is achievable with good PCR tests. This means that, in using them, a small chance that some infected people will not be detected has to be accepted. Real world experience suggests that there is a slightly greater chance of people testing positive and having to isolate where no infection is present. This is fine if you are screening the public – but more of an issue if it’s a key part of your crew or cast that gets sent home unnecessarily.

 The latter problem (specificity) can be addressed using a 2-stage process to PCR test anyone that tests positive on a rapid test. The sensitivity or the rapid testing process is vastly enhanced by REGULAR testing at intervals.  

It’s a strange thing to say when we are, effectively, marketing these tests to clients but rapid testing should probably be regarded as a “better than nothing” measure – i.e., if you don’t have the time (or budget) to regularly PCR test a workforce – rapid tests are much better than doing nothing. However, if you need a highly covid secure work bubble – and infections or isolations would have a major impact on your production – then it’s probably important not to be completely distracted by the cost and apparent convenience of rapid testing and to stick with PCR tests (or even to combine regular PCR tests with rapid tests at shorter intervals).

Why Choose Rapid tests from Location Medical?

As a CQC registered organisation with 25 years of good reputation at stake, Location Medical Services has been highly cautious in rolling out rapid tests - despite huge demand. Although the process seems to be shrouded in secrecy and government is hugely reluctant to publicly “endorse” any one test – we have spoken to numerous companies, trawled through piles of research and validation and, eventually, identified the tests being favoured by PHE & NHS and reviewed all the supporting research. Given that this one test passed all the official trials, it is now gathering more “real world” usage data every day and so we feel this is the only test we would recommend to our clients.  

As with our PCR testing, we have done everything feasible to make volume testing possible and economical with huge discounts for volume and regular re-booked testing regimes.

If you want to discuss your requirements or options with one of our clinical staff – please contact us.

Antibody Blood Tests

These were introduced early on and generated lots of interest. Basically, a blood test to see if you have the Covid 19 antibodies (i.e., if you have had the disease either knowingly or unknowingly). Unfortunately, there is not enough clarity on the protection offered by antibodies, who has them and when they can be measured for antibody blood tests to offer much in terms of helping protect workforces from infection. Even people who have definitely had Covid-19 should adhere to all the normal control measures and no legal or scientifically approved framework exists for allowing cohorts of “antibody positive” staff to operate without covid security in place.

For reference there are some “antibody” (as opposed to antigen) rapid tests on the market. There are also some blood (finger prick) rapid tests. These are not the same thing and, in theory, are part of the rapid test category although seem not to have been favoured by UK government after testing.

Added 19th Feb 2021: Additional Reading: For a well argued cases both for, and against, the widespread use of rapid Covid testing these are peer-reviewed articles from two respected journals (the Lancet & the British Medical Journal) arguing for and against the use of rapid testing in the community.

Covid-19: government must urgently rethink lateral flow test roll out (BMJ)

Clarifying the evidence on SARS-CoV-2 antigen rapid tests in public health responses to COVID-19 (The Lancet)

Form more information & pricing please contact your account manager - (Priority for Existing Clients).

Location Medical Services is a provider of professional medical services to Events, Media, Construction and entertainment industries. For public covid testing services see our public site here. Testing can be carried out at our testing centres - during normal hour of operation - or we can test on site for groups or provide home visit testing for people unable to travel to test centres.

Please note Location Medical Services does not accept any liability for costs, damages or expenses associated with delayed test results - it is the absolute responsibility of the client to ensure that all tests are undertaken with appropriate time allowed before critical deadlines like flight departures or work start dates. Like most pathology tests - both types of Covid test can, very occasionally, produce inconclusive results and retesting will be required to establish infection status.