Getting COVID-19 results within minutes is a no-brainer… or is it? With rapid tests about to be introduced this week in Malta, Fiona Galea Debono gets more information from a distributor, pharmaceutical company PAC3 Ltd.

How rapid is rapid?

It could take as little as 15 minutes and not more than 30 for a result, as opposed to at least a day to communicate the PCR testing in use, a far more laborious procedure.

Reliability?

So, what’s not to like about antigen testing?

Rapid antigen tests are not confirmatory and can never replace the PCR, which is widely accepted by the scientific community as the gold standard testing methodology. But they could work as an additional help, being good for screening to identify those who need a more definitive test.

The difference lies in their sensitivity and how accurately they reflect the truth.

COVID is detected three to four days from infection with the rapid test, as opposed to one to two days through the PCR. This means the latter can be taken between day one and 20, while the former should be carried out between day three and 10.

How sensitive?

It is now above 90 per cent sensitive and specific, reaching 96 per cent sensitivity, which means four out of 100 positive persons swabbed could be false negatives, and 99 per cent specificity, meaning one in 100 could be a false positive.

The higher the rate of infection in a country, the lower the margin of error of the antigen test and the fewer false negatives.

Is positive, positive?

The effectiveness of the rapid test depends on the stage of the disease, but the positive thing is that the positives are positive.

If taken too early, or too late, it could result in a false negative.

When to resort to rapid testing?

During the first wave of the virus, with fewer infections, PCR coped well. But labs have a determined testing capacity per day.

And with more cases and patients wanting a swab, appointments given even days later and concern about whether people would quarantine until then, the time for confirmatory testing on its own may be over and the rapid test could come into use.

Primarily, rapid antigen tests are a tool for mass screening to assist in capturing positive cases early on, rather than waiting for the PCR if there is a backlog at swabbing centres.

They make sense when numbers grow too large for the system to cope – and these are currently at an all-time high.

The screening allows for the early identification of infected people, who can go into quarantine immediately, giving contact tracers a head start, while negative cases can move on to more accurate testing with a PCR.

This could prevent potential positives from running around in oblivion for a while, curbing community spread.

How do the tests work?

The PCR test uses a sample of mucus from a person’s nose to look for the genetic material of the coronavirus. Through a technology called polymerase chain reaction, the viral genetic material, detectable when a person is actively infected, is greatly amplified if present.

Antigen tests, on the other hand, can identify the virus in nose and throat secretions.

They do this by looking for proteins from the virus, which are a direct response to it.

Can I ‘rapid test’ myself?

Like a PCR, most antigen tests require a nasopharyngeal swab – through the nose and the pharynx – and, therefore, the right technique, which needs to be administered by healthcare professionals.

Even simpler versions could provide a fast answer like pregnancy tests, with users spitting into a tube, then reading the results as coloured bars on a strip of paper within minutes.

Can it be bought over the counter?

A rapid antigen test has to be administered by healthcare workers, or a lab.

Moreover, health authorities would want to keep track of who is getting tested and of the results.

Unless there are protocols in place, with data on patients collected and passed on to a dedicated entity, the situation could get out of hand.

The authorities would need to know who has tested positive to ensure they are in quarantine.

GPs and pharmacists may be well positioned to use the rapid tests to assess COVID-19 patients showing clinical symptoms, but protocols would need to be established on who is testing and how, as well as the reporting process.

Where does it make sense to use rapid testing?

The ideal scenario for rapid testing is in institutions like elderly homes, prisons and barracks, where high numbers of people are living together and could benefit from continuous and random screening to catch the positives immediately.

It could also be used to screen people in hospitals, workplaces with many employees and a high level of contact with the public, and other instances where it is important to find out quickly whether someone is at risk of spreading the virus.

Prime Minister Robert Abela has said rapid testing of arrivals could improve arrangements for travellers. Thermal screening at airports, for example, can be bypassed by taking paracetamol for a fever to go down.

Now that schools have reopened and people think they have contracted COVID-19 with every sniffle, cough and runny nose, rapid testing could come in handy too.

Teachers could be randomly swabbed – always following health authority protocols – for their safety and that of their pupils, as asymptomatic transmission could be a spreading factor.

PAC3 Ltd are distributors for SD Biosensor’s antigen test.