Unreliable COVID-19 Tests
The true number of COVID-19 outbreaks is unclear because of inaccurate test results — showing false positives or negatives at times.
According to Professor of Medicine John Bell, “(w)e see many false negatives (tests where no antibody is detected despite the fact we know it is there) and we also see false positives,” adding:
“None of the tests we have validated would meet the criteria for a good test. This is not a good result for test suppliers or for us.”
“There are 100 or more such test kits from different suppliers available for identifying Covid-19 antibodies, and it is important that each of these is checked for accuracy before making them available to the public.”
Live Science reported that negative COVID-19 test results aren’t proof positive of the absence of the disease.
The accuracy of tests used is suspect. “(A)bout 30% of tests…may give false-negative results.”
US Professor of Medicine Dr. Harlan Krumholz said “we have very little public data on the false-negative rate for these tests in clinical practice.”
He and colleagues believe false-negative results may exceed 30% of test results in the US.
Congenial Healthcare’s Dr. Alain Chaoui said many of his patients in the greater Boston area who he “clinically thinks have COVID-19, are testing negative.”
So-called RT-PCR tests are supposed to detect viral genetic material in a patient’s mucus, saliva, and nasal cavity cells bordering the throat.
It’s unclear if false negatives result from faulty testing, incorrect lab analysis, defective test kits, or a combination of the above.
Krumholz said he tells patients with COVID-19 symptoms who test negative that they’re likely infected with the virus and should be treated accordingly, including being quarantined.
The problem with this opinion is that COVID-19 and seasonal flu/influenza symptoms are similar, the former much more contagious than the latter.
Younger people in overall good health with seasonal flu will likely recover in a few days on their own at home by resting and following medical advice.
If symptoms worsen and last longer, illness could be more serious, requiring hospitalization and inpatient treatment.
Massachusetts Department of Public Health infectious diseases director Dr. Larry Madoff said no gold standard exists to judge the reliability of test results.
“Testing may be falsely negative if the test is obtained too early or too late compared to infection, or if the sample isn’t obtained or processed correctly,” he explained.
According to the Mayo Clinic, there’s risk in over-relying on COVID-19 tests to make clinical and public health decisions.
The reliability of RT-PCR tests is suspect. Mayo Clinic infectious diseases specialist Dr. Priya Sampathkumar warned of a likely “less visible second wave of infection from people with false-negative test results,” adding:
“RT-PCR testing is most useful when it is positive. It is less useful in ruling out COVID-19.”
“A negative test often does not mean the person does not have the disease, and test results need to be considered in the context of patient characteristics and exposure.”
In California by mid-May, the most populous US state, Sampathkumar expects about two million false-negative results if comprehensive testing is conducted, posing a serious risk to public health in the state.
Something similar could happen in other heavily populated parts of the US and abroad, including in cities not hit hard so far.
Mayo Clinic recommends the following as long as COVID-19 remains a public health threat:
Continue social distancing, frequent hand-washing, disinfecting surfaces, universal masking of healthcare workers and patients, along with other preventive measures.
Highly sensitive tests or combinations of tests need to be developed and widely used.
Risk levels should be carefully assessed before testing. High-risk people who test negative could be infected because of incorrect results.
Negative tests for low-risk individuals are of less concern than for the above category — though anyone infected can spread disease to others, asymptomatic individuals doing it unwittingly.
Testing is one of many procedures used by Mayo to detect COVID-19 infection.
Some US states only report and maintain positive test results. likely indicating significant underreporting.
For any highly infectious disease, an effective national protocol should be followed to contain the spread of outbreaks.
A separate issue is that individuals diagnosed as disease-free when tested could become infected with COVID-19 days later — meaning repeated tests are needed.
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