Enable Biosciences used the test on 31 people who had recovered after testing positive for coronavirus and compared their results to those of another 25 covid-negative recruits.
According to a yet-to-be-published journal article on the results, the test was more than 99 percent specific and sensitive – two measures of antibody test accuracy that reflect its likelihood to mistake coronavirus for another pathogen, or to miss the infectio altogether.
Antibody tests in the US, so far, have been woefully hit-or-miss, but able to reach consumers because the Food and Drug Administration (FDA) relaxed guidelines to expedite the use of these tests, which are designed to indicate who has already been infected, and may be somewhat protected from reinfection.
The validation study is small, but the company has applied for emergency use authorization from the FDA and hopes that its finger prick test can allow people to collect their own blood from the comfort of home.
Using a lancet like this one, Enable Biotech’s antibody test would let people collect a blood sample from an at-home finger prick, and ship it, dried on a collection card, back to the company’s lab. A small study found the test was 100% accurate (file)
However, their validation study presents the same one that so many other antibody tests have: it’s small.
In a recent interview with DailyMail.com, Dr Susan Whittier, head of Columbia University’s pathology lab said that she received an antibody test that was advertised as being nearly 100 percent accurate.
WHY IS IT DIFFICULT FOR SCIENTISTS TO MAKE AN ANTIBODY TEST SPECIFIC FOR SARS-COV-2?
Coronaviruses invade cells through so-called ‘spike’ proteins, but those proteins take on different shapes in different coronaviruses.
The University of Texas at Austin were able to map the spike proteins of SARS-CoV-2 in mid February – a breakthrough for developing a vaccine.
It was also a huge step forward for scientists developing an antibody test.
There are questions about which antigens (proteins) are best for an antibody test target, ‘although the viral spike protein is universally perceived as the obvious candidate’, Anna Petherick, a lecturer in public policy at University of Oxford, wrote in The Lancet.
Which part of the spike protein to use is less obvious, and is causing difficulty in creating a reliable antibody test.
‘There is a lot hanging on the uniqueness of the spike protein,’ Ms Petherick said.
‘The more unique it is, the lower the odds of crossreactivity with other coronaviruses— false positives resulting from immunity to other coronaviruses.
‘The most similar of these is severe acute respiratory syndrome coronavirus (SARS-CoV), which led to the SARS outbreak of 2002.
‘But another four coronaviruses cause the common cold, and ensuring there is no cross-reactivity to these is essential. ‘
A team at New York’s Icahn School of Medicine at Mount Sinai (NY, USA), has published details of antibody tests that use either the whole spike protein.
Others, such as Peng Zho at the Wuhan Institute of Virology in China, who was part of the team that sequenced SARS-CoV-2’s genetic code, have used the nucleocapsid protein and the spike protein.
‘[The] nucleocapsid protein is the most abundant viral protein, which means it’s easy to detect. But we also chose spike protein because it’s very specific,’ Dr Zho said. ‘Actually, for coronavirus, the most divergent protein is [the] spike protein.’
When she read the fine print, it had been tested on ‘like, five people,’ she said.
‘That’s crazy,’ she said. ‘Normally that would never happen, but in the middle of a pandemic, you’re allowed to push assays out because maybe perfect is the enemy of good.’
Currently, the FDA lists 13 antibody tests it has authorized and, in recent weeks, it’s begun removing and sending letters to makers of tests that it has reviewed and deemed too unproven for use.
But that didn’t stop them from getting to market and selling to Americans, who might have been misled to believe they had some antibody protection against reinfection – though it remains unclear whether or how much immunity coronavirus antibodies confer – by th inaccurate tests.
Blood samples to be analyzed for these tests still have to be collected by a health care provider before they are run in a lab.
For some, that may discourage getting tested, because healthcare settings themselves are high-risk environments for coronavirus exposure.
Enable wants to change that.
The biotech firm developed a blood test for antibodies that was 100 percent sensitive and 99.6 percent specific in their tests that used blood collected 15 days after people developed COVID-19, and sent an application for its authorization to the FDA several weeks ago.
Around the same time, they began recruiting participants for a validation study to see if their test performed as well when tasked with analyzing a dried blood sample.
Dried blood samples could be collected at home and shipped to labs more cheaply and perhaps with less risk of damage or contamination.
The company has now recruited some 150 volunteers locally and across the country.
On Monday, it posted a pre-review copy of the results of testing 56 of those volutneers – 25 who were covid-positive but had recovered and 31 who had never had the infection.
They had the volunteers use their kit, which includes a finger prick collection kit.
They had to put between two and five blood spots on a collection card to dry. The cards contain preservative that keeps them safe for transportation.
Participants then simply mailed them back to the San Francisco lab.
According to the pre-print, the testing was 100 percent sensitive and specific, returning positives for everyone who had already been confirmed to have COVID-19, and negatives for those who hadn’t.
‘This methodology allows people to get a high-quality test performed by laboratory professionals from the safety of their own home,’ wrote co-founder and CEO Dr Peter Robinson in a Monday blog post.
‘In fact, with the fully-volunteer cohort we have tested so far, we report 100% accuracy of the test, even for kits sent in from as far as the east coast!’
He added that the company is in early talks with the FDA about approval of the test.
Source: Daily Mail | Health