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Coronavirus: Up to third of antibody tests give false negatives

There is little to no evidence proving the accuracy of coronavirus antibody blood tests, a new report suggests.

Researchers reviewed dozens of studies looking at antibody kits, which determine whether or not someone has previously been infected by the virus and has built up an immune response.  

Specificity rates ranged from 66 percent to 97.8 percent, meaning the test may return false negative up to one-third of the time.

What’s more, commercial test kits were more likely to miss cases than those conducted in a lab. 

The international team, led by McGill University Health Center in Montreal, Quebec, Canada, says the findings should make governments rethink about issuing ‘immunity passports’ to get people back to work and shore up the economy.

In a new study, researchers found that sensitivity rates, meaning the rate at which tests come back positive, ranged from 66% to 97.8%. Pictured: Medical staff from myCovidMD provide free COVID-19 antibody testing at Faith Central Bible Church, in Inglewood, California, June 19

In a new study, researchers found that sensitivity rates, meaning the rate at which tests come back positive, ranged from 66% to 97.8%. Pictured: Medical staff from myCovidMD provide free COVID-19 antibody testing at Faith Central Bible Church, in Inglewood, California, June 19

In a new study, researchers found that sensitivity rates, meaning the rate at which tests come back positive, ranged from 66% to 97.8%. Pictured: Medical staff from myCovidMD provide free COVID-19 antibody testing at Faith Central Bible Church, in Inglewood, California, June 19

This means between 2.2% and more than one-third tests may return false negative results. Pictured: Nurse Christina poses with a nasal swab at JFK International Airports Terminal 4, the first airport-based COVID-19 testing facility in the US in New York City, June 29

This means between 2.2% and more than one-third tests may return false negative results. Pictured: Nurse Christina poses with a nasal swab at JFK International Airports Terminal 4, the first airport-based COVID-19 testing facility in the US in New York City, June 29

This means between 2.2% and more than one-third tests may return false negative results. Pictured: Nurse Christina poses with a nasal swab at JFK International Airports Terminal 4, the first airport-based COVID-19 testing facility in the US in New York City, June 29

‘These observations indicate important weaknesses in the evidence on COVID-19 serological tests, particularly those being marketed as point-of-care tests,’ the authors wrote.

For the report, published in The BMJ, the team looked at 40 studies evaluating the specificity and/or sensitivity of antibody tests. 

Sensitivity is how often the test correctly determines people who’ve been infected in the past and specificity is how the test identifies those who’ve never been infected.  

Of the 40 studies, assessed, more than 70 percent were China, with the rest from Denmark, Germany, Japan, Spain, Sweden, the UK and the US. 

Half of the studies were not peer-reviewed and the majority had a high or unclear risk of bias, meaning study design problems that can affect findings. 

Only 10 percent of the studies analyzed included outpatients and just two looked at tests administered at point of care.

The sensitivity rate, meaning how often they gave a positive result, ranged from 66 percent to 97.8 percent. 

This means that between 2.2 percent and 34 percent of patients get results that say they don’t have antibodies when they actually do.

Additionally, sensitivity rates were lower among commercial test kits than those conducted in a lab, at 65 percent versus 88.2 percent. 

Sensitivity rates were also lower among tests performed in the first or second week from symptom in comparison with those performed after the second week.

The team says the ‘poor performance’ of antibody tests ‘raises questions’ about using them when making medical decisions.

Researchers added that the results ‘should also give pause’ to any governments considering using the results of antibody tests issue so-called ‘immunity passports.’

‘Higher quality clinical studies assessing the diagnostic accuracy of serological tests for COVID-19 are urgently needed,’ the authors wrote. 

‘Currently, available evidence does not support the continued use of existing point-of-care serological tests.’

Source: Daily Mail

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