A study found that the antibody test for COVID-19 has very low accuracy.
Mayara Lisboa Basto of McGill University Health Center in Montreal, Canada, says that serological [blood] tests for COVID-19 are not accurate.
According to the research, point-of-care tests, performed outside the laboratories, are especially inaccurate. They often give wrong results about whether someone is COVID-19 positive or not. Bastos and colleagues asked health officials to stop these types of tests.
Study: Accuracy of Antibody Testing
The team analyzed data from 40 studies on sensitivity and/or specificity of these tests.
Test sensitivity is actually the ability of a test whether it can identify the disease correctly or not. It is the rate of correct positive results. Conversely, test specificity is the correct negative testing ability of a test.
70% of the studies were from China; while the other 30% were from United States, United Kingdom, Japan, Denmark, Germany, Spain and Sweden. The researchers said that most of the studies had problems in the design and half of them were not peer-reviewed; this may had influenced the test results.
Only 4 out of 40 studies included outpatients in the analysis and two studies evaluated results of the tests at the point of care.
Also Read: When To Get Tested For COVID-19?
The result for sensitivity in all the studies ranged from 66% to 97.8%. It was dependent on the method of testing. Consequently, testing methodology missed 2.2 to 34 percent patients who probably had infection.
The results for specificity ranged much higher, about 96.6 to 99.7 percent. This was dependent on the type of test. Therefore, testing reported 3.4% to 0.3% of patients falsely positive.
The sensitivity results rates were especially lower for lateral flow immunoassay (LFIA) as compare to other tests. Authorities consider these tests as “immunity passports”; they allow people to return to their work.
We can understand the danger with the following example. If LIFA test gves 10% 10% COVID-19 positive rate for a population; 31 out of 1000 people whom the virus never infected, will appear as ‘immune’. In the same condition, 34 out of 1000 infected people will be reported as ‘healthy individual[s]’.
The sensitivity results were lower using commercial kits as compared to non-commercial kits. It was about 65% for the former while 88.2% for the later.
The sensitivity level also varied with time of start symptoms. It was lower within the first and second week of appearance of symptoms as compared to the period afterwards.
The team believes that the findings have to be confirmed in hospitals again; as the researches had some uncertainties.
Dr. Amesh Adalja is an infectious disease physician. He is also one of the senior scholars at the Johns Hopkins Center for Health Security, in Baltimore. Adalja agreed with the results of the study. He said that serological test method is very interesting. Yet health agencies should consider it that many test kits out there are not reliable and may give inaccurate results.
The new review “underscores the need to standardize how these tests are interpreted, what are the acceptable sensitivity and specificity parameters, and how test results can be operationalized,” Adalja said.