There are a number of different COVID-19 testing systems coming onto the market. The questions that most commonly arise are how accurate the differen testing methods are, and are whether they are suitable for the needs of patients. Here we will provide some clarification about selected covid-19 testing methods and their use.
What Types of COVID-19 Tests are Available?
Firstly, we need to understand the requirement for antigen testing. An antigen test identifies the current presence of an active infection. The reasons patients require a COVID-19 test fall into different groups:
COVID-19 Testing for Travel
Many countries require evidence of a negative COVID-19 antigen test before departure at the airport or arrival into the country of destination. Some countries are more specific and require these to be of the molecular test type only (PCR Test). All countries requiring a test will require these to be completed within a defined time limit prior to departure. They will require evidence of the negative result supplied as a travel certificate. Information on the test result certificate needs to show the accreditation of the laboratory.
The key characteristics when choosing a COVID-19 test for travel
- Time before departure – will your testing provider return a result within the required time before departure i.e. <48 hours / <72 hours?
- Standard of testing – is the testing undertaken by a laboratory that has an accredited standard and registered by the United Kingdom Advisory Service (UKAS)?
- Accuracy – does the manufacturer indicate their sensitivity and specificity accuracy data?
- Certificate – will the testing facility provide a test result certificate for travel?
- PCR testing – is the test method using a PCR (for those countries requiring it)?
A COVID-19 test may be requested by an employer when a patient is returning to work or starting a new job. The type of test required can be antigen or antibody, but are more routinely requested as antigen tests, which tests for an active infection. As above, employers usually require evidence in the form of a test result certificate.
Identification of an Active Infection
This is the role for the NHS testing service, and this should be regarded as the first point of contact. Some private testing is available; however, the testing may take place in areas (e.g. pharmacy, surgery) where there is a possibility of a high presence of infection from carriers or super-spreaders.
Types of COVID-19 Tests
The samples for testing can be collected by a variety of different means e.g blood, swabs or saliva. As the virus can be found in different places in the body at different times then a 2-stage collection, for example throat and nasal swab, as used at Nomad, are better than a single site or saliva test.
There are 4 main testing techniques:
Molecular Test (RT-PCR /TMA) or PCR Test are regarded as the gold standard. PCR tests have the lowest levels of false negatives and false positives. PCR tests are accepted throughout the world by all countries for travel certification purposes and for occupational health. The Express PCR Test provided by Nomad uses a 2-stage collection and external registered laboratory to test all our clients samples.
Rapid Antigen tests are the new rapid antigen testing system which provides rapid results with accuracy levels that are the closest to the PCR test. The Rapid Antigen Test can provide a result within 15 minutes and can be suitable for travel to those countries requiring a negative COVID test only (not a negative PCR test). Due to it’s rapid result, the Rapid Antigen Test is also ideal for occupational health and return to work purposes.
LAMP (as used at Heathrow airport) is currently being trialled for rapid testing but only acceptable to countries not requiring a PCR test for entry. LAMP test is new technology, and the accuracy is still being assessed in clinical settings. This test is also being considered for testing patients upon arrival.
Immunofluorescence is a different type of testing method producing a quick response to identify a current infection but with a lower level of accuracy. This type of test is not suitable for use in travel as if it is not conducted at an external laboratory. According to some manufacturers there is a potential for cross-reactivity when performing multiple tests and false readings if secondary sources are detected. This can result in the workflow being less flexible and more expensive.
Comparison of accuracy between COVID-19 tests
|Rapid Antigen test4||96.2%||99.2%|
Sensitivity is the ability of a test to correctly identify those with the disease (true positive rate), whereas specificity is the ability of the test to correctly identify those without the disease (true negative rate)
COVID-19 Laboratory Testing Standards
When considering which laboratory to use for testing, consideration needs to be given to the registration of the laboratory and the standards they use. In the UK the governing body is UKAS and all labs should be registered with them. These labs operate to specific standard processes called ISOs which maintain the quality assurance of the testing.
There are different needs for each COVID test, and these will range from the simple diagnostic test to the complex needs of travel testing. For the highest levels of accuracy, with proven medical evidence the PCR test is the highest standard. For travelling purposes, the service should provide a turnaround time that will allow for a written certificate of COVID free status.