Corona Daily 342: Testing Times

Since the time life became surreal, the world has been in a tearing hurry to end the nightmare. State health regulators committed serious compromises. In April, America’s Food and Drug Administration decided to approve tests without reviewing their safety and effectiveness data. The US market was flooded with poorly performing tests.

In March, the UK bought 2 million unproven finger prick tests from China, which Boris Johnson advertised as the “game changer”. In April, an Oxford study confirmed the tests were too inaccurate to be used. In May, a new antibody test from Roche was reported to be 100% accurate. Public Health England showed that the test couldn’t identify 16% samples who had suffered from covid-19. In June, MHRA (Medicines and Healthcare Products Regulatory Agency) banned sales of several tests, including all finger-prick tests. (Antibody tests either draw blood that is sent to the lab, or are rapid finger-prick blood tests.)

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Wrong/unproven drugs/vaccines can cause damage, occasionally kill. Hydroxychloroquine was given an emergency authorization under political pressure. Later when it was clear the possible heart damage outweighed any benefits, the authorization was withdrawn. Tests don’t kill directly, so the regulation is more lax. The world over, Covid-19 tests are prone to give wrong results because the regulatory process is weak, and inadequate. Approvals are issued based on self-declaration rather than scientific scrutiny. This is particularly true of antibody tests. An expert panel in the USA examined 9500 papers describing test validation and found only 47 worth considering. The UK has not approved any at-home tests. Several people offering tests are arrested, and over 47,000 tests have been seized.

Generally, after many tests, follow-up testing is recommended. Canada, with fewer people and ample resources insists on two virus tests. The first result is called presumptive and second confirmatory. The result is confirmed only when the two tests match. Neither such luxury nor the required resources exist in most parts of the world. The world is living with false positives and false negatives.

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Antibody tests for Covid-19 have largely been unreliable, inaccurate and devoid of meaning. They may look for the wrong antibodies, the timing of the test may be wrong, or the right antibodies may fade away. For people from low-prevalence areas, the test gives a large number of false positives. (Even without doing the test, we know the probability of having antibodies, and not having them, is 50% each.)

There is a global consensus among doctors and healthcare experts that antibody tests should be used only for checking the virus spread in the community, not for testing an individual. Due to poor controls, and unreliability, a positive result may create a sense of false security.

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To make matters even more exciting, CDC (Centers for Disease Control and Prevention) admitted they were mixing the results of viral and antibody tests. That way USA could show a higher number of tests done. Mixing the tests makes it much harder to understand the meaning of “positive” tests (in a viral test, one hopes to be negative, in antibody test, the reverse). Virus testing shows the number of people infected, whereas the antibody testing is compared to a rearview mirror. A Harvard professor of global health called it a total mess.

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In short, avoid an antibody test, unless you are taking part in a population survey where you live. If for some reason you must give blood to check antibodies, please ask the service provider about the regulatory approval they have got.

Abandoning scientific method in crisis times simply creates additional crises.

Ravi