WE KNOW pregnancy tests are accurate because those who test positive become clearly pregnant. We know a bacterial throat culture is accurate as a diagnostic tool because those who test positive have symptoms of strep throat.
We do not know that the Covid-19 tests are accurate because many who test positive have no symptoms. Furthermore, the tests do not detect the presence of a virus that has been purified, isolated and tested for infection in laboratories. Nor is there a distinctive set of symptoms for Covid-19.
The inventor of the often-used Polychromase Chain Reaction (PCR) test stated that it was not reliable for detecting viral infection. It was designed for an entirely different purpose.
Torsten Engelbrecht and Konstantin Demeter give a critical overview of problems with the PCR test. For readers who want a more detailed look, these two podcast interviews, “Simplifying PCR” and “Stephen Bustin on Challenges with RT-PCR,” by David Crowe go into the subject at length.
The other common diagnostic tool is an antibody test.
Crowe examines the antibody test in an article available online. He writes:
Antibodies are our body’s immune system reaction to viral proteins, known as antigens. Antibody tests incorporate antigens, and a chemical that allows the intensity of the reaction to be measured using light. Ideally antigens would come from pure virus, but COVID-19 virus has never been purified, thus antigens are created artificially from proteins based on portions of the 30,000 base RNA genome that is believed to come from the virus.
The major antibody types that are looked for are IgM, believed to be a generic infection fighting antibody that arises about a week or so after infection, and IgG, believed to be more specific, and believed by some to take longer for the body to create. After the infection is resolved, IgM antibodies are believed to gradually disappear, while IgG remain, providing ongoing immunity.
Unfortunately, this idealized picture is not supported by the available evidence, either because the evidence does not exist, is insufficient, or because it directly contradicts the model. Positive antibody tests should be impossible before the person is first infected (RNA positive). Yet, old blood samples (2019 or before) have tested positive in significant numbers. Almost 14% of saved blood from old donations tested positive in a Dutch study, and in the validation of the Cellex and Chembio tests, 4.4% and 3.6% of old samples were positive.
Your head might start to spin when you get into the details.
Here is a take-away everyone can agree on: A scientific consensus on the reliability of these tests does not exist.