Serology study appears to support GPs’ hunch on coronavirus testing

Matt Woodley

16/09/2020 4:24:53 PM

Up to 60,000 COVID cases may have been missed during the first wave of the pandemic, supporting the idea that testing criteria were not wide enough.

Taking blood
A new pre-print study from the Australian National University has revealed up to 71,400 people may have contracted the virus by July – higher than the then national total of 11,190. (Image: ANU)

As far back as January, GPs were concerned COVID-19 cases were being missed due to overly-restrictive testing criteria.
Those fears may have been well founded, as a new pre-print study from the Australian National University (ANU) has revealed up to 71,400 people may have contracted the virus by July – far higher than the then national total of 11,190.
This estimate was extrapolated from 3000 blood samples provided by healthy Australians awaiting elective surgery between 2 June and 17 July, which were then run through a dual antigen enzyme-linked immunosorbent assay (ELISA).
The new form of COVID testing revealed 0.24% (eight people) were positive for coronavirus antibodies, despite none having previously tested positive to the disease.
While yet to be peer-reviewed, the study’s co-lead researcher Professor Elizabeth Gardiner told newsGP the authors are ‘very confident in the sensitivity and specificity’ of the new test.
‘This serology is really that footprint of what was happening back in March and April [and indicates] that we didn’t really have a good handle on it,’ she said.
‘GPs probably won’t be surprised by that.
‘We kind of always knew, because the testing was initially limited to people with two or three symptoms … [but] the asymptomatic group exists out there and is probably able to spread the virus.
‘[Unfortunately] we really don’t have a good handle on how predominant they are and whether they’re driving the second wave that we’re seeing.’
However, while the researchers are confident in the test, antibody-testing expert and director of the Burnet Institute Professor Brendan Crabb told The Age the estimate of 71,400 infections is ‘on the high side of likelihood, but not out of the realms of possibility’.
He also pointed out the antibody test has a false positive rate of 1.09%, so ‘there is still much margin for error here’.
Funding permitting, the ANU researchers are hoping to expand the study in order to capture a sample size large enough to accurately estimate COVID prevalence nationwide and help reduce the study’s large confidence interval.
Should this occur, Professor Gardiner said general practice would be ideally placed to contribute.
‘We would love to expand the study and look at other groups across Australia,’ she said.
‘If we could harness the power of the GP, who is right down at the coalface with people and could consent them to be part of the study, that would alleviate a lot of the logistical challenges.
‘The onus would be on the GP to select the patient – we couldn’t just have a “Come one, come all [approach]”.
‘We would need an accurately annotated clinical history, basics around contacts with travellers, co-morbidities, age [etcetera] … so that we could stratify the groups.
‘We’d be able to evaluate antibody responses across age groups. That’s really a big unknown, and that would be something we could get a handle on in Australia.’
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Dr Fiona Jane Henneuse-Blunt   17/09/2020 11:47:13 AM

I have always maintained that I could name half a dozen patients who I have strong suspicions could have had Covid 19 back in Jan/Feb. Most had travelled through China but not Wuhan. All were really sick. Some hospitalised. All negative for respiratory viruses. All ineligible for Covid swab. I wonder if I even had it myself?! We weren't wearing PPE yet and I had a week off with gastro and 3kg weight loss in that week. Who knows? Maybe. I would love to be able to offer those patients a serology test.

Rural GP   17/09/2020 12:22:31 PM

Oh the value we could add in General Practice.!
You will need deep pockets, I am afraid.
Please don't join the queue and rely on the goodwill of stretched GP's