Rapid test kits are like toss-coin exercises | Lifestyle.INQ

OCTOBER 27, 2022

President Duterte has ordered the procurement of rapid test kits for the new coronavirus disease (COVID-19) despite the lack of evidence of their usefulness in detecting early cases in community-wide screening.

We appreciate the President’s strong political will to implement hastily what he believes is the best for the country in times of exigency. He shrugs the uncertainties aside, probably thinking that inaction is worse than making a wrong decision.

The President says he’s no expert on this problem, so he listens to the advice of bright minds in this field. But most of the bright minds on this subject say that using the available rapid test kits is convenient, but could be a “recipe for disaster” if used without proper guidelines.

I’m not sure if the Department of Health will be convinced to implement community-wide mass testing using the rapid test kits, to test people even if they show no definite symptoms, or have just started to show symptoms.

I hope the procuring agencies won’t fall into the trap of buying expensive but unvalidated rapid test kits.

Occasionally I get email messages from foreign manufacturers of these kits, with prices ranging anywhere from $1 to $12 per kit, depending on whether it’s validated or not.

Manufacturing the test kits is easy; what’s important is that they’re validated to be accurate and sensitive. Validation can take time and money, so the validated ones cost more.

The COVID-19 rapid test kits are very similar to pregnancy test kits; you can see the results in a few minutes, but interpreting them can be tricky. So, it’s not something that should just be given out and left to the individual to do and interpret.

Granting that the government will procure the validated test kits, does that make them reliable and cost-effective? This will still depend on what types of individuals you do the test on.

If you do the test on asymptomatic people, simply on the basis of exposure, or because there is an increasing number of confirmed COVID-19-positive individuals in the community, it may not be that useful, and not worth the dollars we spend.

When resources are limited, we want to get the biggest bang for the buck. And spending hundreds of millions on rapid test kits may not give us that bang we’re looking for, or what we could have gotten had we allocated it for something else.

50 percent

If we use the rapid test kits for mass community screening, there’s a much cheaper and just as reliable or unreliable way to do it. The government doesn’t need to spend anything on it; perhaps, just one P10 coin per barangay is all it needs. It’s simple: You just toss a coin, heads means COVID-19-positive, tails means COVID-19-negative.

Without clear guidelines on who these rapid test kits will be used for, the sensitivity to diagnose someone with COVID-19 is at best 50 percent. That means you’ll only diagnose half the cases, and miss the other half. If you include those, the tests will falsely diagnose as positive—probably due to a wrong interpretation of the results—and the reliability will be even less than 50 percent, so, you’re better off just tossing a coin.

This is likely the reason Carlito Galvez Jr., head of the Inter-Agency Task Force for the Management of Emerging Infectious Diseases, also announced after the President made his “I’m taking the risk” announcement that the government will also purchase something like 900,000 polymerase chain reaction (PCR)-based kits, so they could validate the results obtained from the rapid test kits.

In that case, we’re unnecessarily increasing our expense. We might as well just do the standard PCR testing. When I was taking my MBA a long time ago, our professor would say, “Isip-isip, para hindi madoble gastos!” PCR tests for COVID-19 are far more accurate than rapid test kits, though it takes some time to get the result. The problem is that we still have only a few accredited laboratories who could do them. We might just as well invest whatever money to increase our capacity to do more PCR testing, which is still considered the gold standard.We have many laboratories in the country with the machine to do reverse transcription (RT) PCR-based tests, but as Dr. Edsel Maurice Salvaña, director of the Institute of Molecular Biology and Biotechnology, National Institutes of Health, University of the Philippines, clarified in our column a few weeks ago, they also need the proper safety infrastructure, standard operating procedures for emergencies, a properly trained staff, even flu vaccines for all their employees. A misstep could have disastrous results.

The RT-PCR tests diagnose COVID-19 by detecting the presence of viral material during infection. It’s more sensitive in diagnosing cases in the early phase of the infection.

Several days

The rapid test kits detect the antibodies produced by the body as a reaction to the virus infection. It takes several days for the body to develop these antibodies. If we use it for community screening in asymptomatic individuals, even if they already have the virus but it’s still early, and the level of antibodies produced is still too low for the test kit to detect, we’ll get a negative result.

The problem is that one who falsely tests negative would have a false sense of complacency—and will most likely spread the virus in the community.

The uncertainty with the currently available rapid test kits arises from the fact that none of them uses the industry-standard plaque reduction neutralization test (PRNT) assay, explains Dr. Salvaña. The PRNT measures more accurately the titer of antibody for a virus. The other rapid test kits fall short of the PRNT standard.

A colleague who advocates the use of rapid test kits for mass screening says that if you correlate the results of the rapid test kits with a good medical history, including a detailed description of the patient’s symptoms, you’ll be able to diagnose cases even if you get false negative results from the test. Precisely! We don’t really need the test if the patient already has typical symptoms. Regardless of what the test result is, we’ll still treat the patient as a COVID-19 patient. We should treat the patient, not the lab result.To be fair, though, the accuracy of the test increases remarkably by the second week, and these test kits should be able to confirm the diagnosis by then. I find a rapid test kit more useful as a predischarge test, or during follow-up, to check if the COVID-19 patient has developed the antibody (IgG) against the virus. The presence of the antibody protects the individual; he has the antibody to fight off the virus. That’s why his plasma (part of his blood) could be used to help a critical COVID-19 patient, who has not developed the antibody yet, survive his or her own infection.

If the purchase has already been made for the rapid test kits, so be it. But I hope the President listens to the right bright minds around him, and makes sure that the test kits are used properly based on recommended guidelines. He doesn’t really have to take unnecessary risks. I’m reminded of the admiral of the United States Navy during the American Civil War, who ordered his men, “Damn the torpedoes, full speed ahead!” I don’t recall what happened to his fleet after such bravado. INQ

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