From Fardistanthills - a great put-down for today’s dear person.23 Feb 2021 20:50
I'm a chemist - or was - long retired - and worked in a completely different field. But from my experience, and as Monkswood implies, I would be more than a bit surprised if PD scientists had got their assessment procedures wrong! And I would be surprised if AVCT had allowed PD to get their assessment procedures wrong, vis a vis the freezing issue for example. These guys on both sides are all top class.
Also I keep seeing posts in which it is claimed that PD have failed one or other of AVCT's LFDs? Seemingly this arises from what unidentified sources told HuffPost over the weekend. I would take this with a largish pinch of salt - nothing disclosed by AVCT in their RNSs can be read as their having had an LFD failed by PD.
On the contrary this Mondays RNS correcting the HuffPost's weekend piece says: "The press report this weekend incorrectly stated that a saliva-based rapid antigen test from Avacta had been evaluated at Porton Down. In fact, the evaluated test was the anterior nasal swab test that has subsequently generated the excellent initial clinical performance."
So which test is supposed to have been failed by PD and in what way? Based on this and all previous RNS disclosures, the short answer seems to be none. OK, maybe some imaginary, undisclosed ones - in the eyes of those that speculate - and take what they read in the press as gospel!
The other thing that appears to have been misunderstood from the Monday RNS is the statement "in its evaluation Porton Down used artificial samples and did not use clinical samples."
This ties in with normal practice. The initial step in proving up even the simplest of new analytical procedure is to use an 'artificial' or spiked samples. It allows the early assessment of a new test to be done under controlled conditions, which eliminate all the real world noise that will subsequently be encountered when samples are taken 'in the field.' In the case of a medical diagnostic test such as AVCT's LFDs, these 'in the field' samples are the clinical samples that are now undergoing what Monday's RNS calls 'full clinical validation with a larger number of patient samples in order to obtain a CE mark for the test for professional use'.
So reference to the use of 'artificial' samples by PD was reference to an initial evaluation, which would have deliberately avoided the use of real clinical samples - in order to eliminate real world variables - in order to focus on pure analytical performance.
Hope this helps, somewhat.