COVID-19 testing for the workplace – update 19th August 2020
Whilst plans are underway for employees to return to the workplace across the City following easing of lockdown restrictions and a fall in COVID-19 infection rates, the role of antigen and antibody testing is widely being considered to ensure the safety and wellbeing of employees.
Our current advice, which is subject to change as more information becomes available, is that the weaknesses of mass testing outweigh the benefits. This article explains the reasons. We are able to support employers who may wish to progress with testing employees, as long as the risks and weaknesses are clearly outlined and understood.
Antigen testing (the “do I have it” test)
COVID-19 antigen testing by polymerase chain reaction (PCR) determines if an individual is currently infected with COVID-19. The test involves nasopharyngeal (nose and throat) swabbing and is recommended within the first few days of an individual becoming symptomatic, when the viral load kinetics are thought to allow the virus to be more accurately detected.
The COVID-19 antigen test has been found to have up to 30% false negative rates – so up to 30% of truly positive cases can be missed. To put it another way, 1 in 3 negative test results may be incorrect. That in turn means that some people given a negative result may still be infecting other people, even if they don’t have any obvious symptoms.
There are various factors that could contribute to this problem, including the timing of the test and the sampling procedure. Nasopharyngeal swabbing is generally found to be unpleasant, can trigger gagging and this in turn can often result in a poorly obtained sample. A poorly obtained sample can then lead to an incorrect test result.
Whilst a positive result carries weight, a negative result cannot fully exclude COVID-19 infection. Other factors, including the pre-test probability of COVID-19, according to symptoms and risk of exposure are the primary considerations that need to be taken into account.
If the pre-test probability of COVID-19 is high (because of symptoms or potential exposure to a confirmed case) that individual should still self-isolate, even if they receive a negative antigen test result, which is the current Public Health England (PHE) guidance.
COVID-19 antigen testing as a screening tool is currently not widely recommended. Any screening test needs to demonstrate that it is accurate, that early detection of a disease or disease marker can significantly reduce adverse outcomes, whilst also being cost effective.
The benefit to employers of regular COVID-19 antigen testing undoubtedly is the early detection of cases, especially in asymptomatic individuals, which could allow the workplace to take adequate measures to protect other employees who may have been in contact with them.
There may also be a sense of confidence in employees returning to the workplace that their colleagues are being regularly tested for COVID-19 and that their risk of exposure may therefore be lower.
The drawback is that a negative test cannot 100% rule out COVID-19 infection. A negative test on a Monday may not necessarily mean that individual could not have COVID-19 infection by Thursday.
There is currently no official guidance on the frequency that any such testing should take place, which means that any workplace testing programme will not be a risk-free path for employers. Testing frequently drives up costs, for potentially little additional benefit, whilst extending the testing period increases the risk of missing infectious cases.
Any employees with symptoms of COVID-19 should self-isolate (as per PHE guidelines) and seek testing, either through a private provider or through the PHE government website, where free testing can often be arranged on the same day, in a local drive-in centre. Free “at home” testing kits are becoming widely available for delivery by the following day.
If any positive results are found, measures must then be taken to track and trace all the contacts of any known positive cases. The government’s track and trace service has been criticised by some in recent weeks, however, it is likely to be a far more reliable path for employers than trying to facilitate any in-house approaches to contact tracing.
PHE has made QR codes for any location freely available and encouraging employees or visitors to scan the code using the NHS Track & Trace app (when it becomes widely available) is likely to be a very helpful step.
Antibody testing (the “have I had it” test)
COVID-19 antibody testing determines if an individual has been exposed to COVID-19 in the past at some time. PHE has approved tests provided by Abbott and Roche and venous sampling methods (taken by a healthcare professional from a vein) have been found to be the most accurate approach. “At home” testing kits are not currently recommended.
Initial analysis of the antibody tests has determined that timing is key to the accuracy of the test. The ideal time to test for antibodies is between 14 and 40 days from the onset of symptoms, based upon currently available information.
Antibody tests can also result in false negatives and factors contributing to this may be the timing of the test, the initial severity of COVID-19 symptoms and the age of the patient. Fortunately, a false negative result does not pose a risk to an individual or their contacts, as the antibody test is only a marker of past infection.
A positive result indicates some level of immunity to COVID-19, however, we still do not yet have the data to confirm how long any immunity lasts. We still also do not know whether an individual who has COVID-19 antibodies can be re-infected, or whether they may still be able to transmit the virus or not.
Assuming an employee with the confirmed presence of COVID-19 antibodies is protected from COVID-19 infection, or possible onward transmission, at this stage, is clearly not recommended.
The current value of antibody testing is to provide public health data on the extent of disease spread. On a personal level, the benefits of antibody testing are likely to increase markedly, once we know more about how long immunity is conferred.
Whilst there is some value in both COVID-19 antigen and antibody testing for employees returning to the workplace, this should not replace measures to facilitate social distancing, hand hygiene and adhering to self-isolation guidance for individuals and their households should they develop symptoms.
Risk assessments (which can be delivered quickly and remotely) are the most essential first step to identify those individuals in vulnerable categories, allowing their workplace requirements to be assessed and planned on an individual basis.
It is prudent to consider identifying a safe location to be used as a potential quarantine location in any office or workplace, in case an employee presents with symptoms whilst as work. Please contact us for any further advice regarding infection control or managing PPE for employees.
Based upon the currently available information, London City Healthcare consider that the costs and benefits of mass testing for employers are not equally balanced.
The weaknesses inherent in the currently available PCR tests suggests that mass testing will not be effective in mitigating the risks to employers. Accessing the government-funded testing service, as soon as symptoms present, is currently the most cost-effective approach.
Because the only outcome of antibody testing is providing information and exactly what that information means is so uncertain, we would not generally advise mass antibody testing for the workplace, unless the employer or employee has a clear interest in understanding their own health.
Dr. Sidra Malik BMBS MRCGP DFSRH DRCOG
18th August 2020