Apparently I cannot say this loudly enough
The recent @bmj_latest articles by @deeksj et al deriding Rapid Ag Innova Tests are simply WRONG
They simply do NOT appropriately interpret Ct values & do NOT consider massive importance of how long PCR remains + post-infectiousness
The recent @bmj_latest articles by @deeksj et al deriding Rapid Ag Innova Tests are simply WRONG
They simply do NOT appropriately interpret Ct values & do NOT consider massive importance of how long PCR remains + post-infectiousness
Inspection of Ct values among the Asymptomatics & correlation to RNA copies / ml shows Ct values in Liverpool are ~8 lower than often seen in literature. The failure to recognize this means the estimates of Ag test sensitivity for "high virus" are totally off.
2/x
2/x
The sensitivity for "moderately high" or "high" viral loads in the Liverpool data are ~90% and ~100%.
But to know this you cannot just assume a Ct of 25 elsewhere (often described as entering "high viral load") means same thing as a Ct value in other labs.
3/x
But to know this you cannot just assume a Ct of 25 elsewhere (often described as entering "high viral load") means same thing as a Ct value in other labs.
3/x
In the Liverpool data, a Ct value <18 or so should be considered similar to Ct ~25 in many other papers. This is reflected across numerous data streams when you do the right analysis.
@deeksj et al entirely missed this and instead have spewed misinformation to the globe.
4/x
@deeksj et al entirely missed this and instead have spewed misinformation to the globe.
4/x
Where @deeksj suggested incorrectly that the Innova test had a 66% sensitivity for "higher viral loads" what they would have found, given correct analysis, is the sensitivity was >90% for higher viral loads, and in that study, found to be 100% in the highest viral loads.
5/x
5/x
Further, the analyses fail to properly account for long duration of PCR post contagiousness
When evaluated correctly, a priori we EXPECT a test for infectiousness to have a Max sensitivity of ~40% among Asymptomatics (20% - 60% depending on if outbreaks going down or up)
6/x
When evaluated correctly, a priori we EXPECT a test for infectiousness to have a Max sensitivity of ~40% among Asymptomatics (20% - 60% depending on if outbreaks going down or up)
6/x
This is bc average duration of PCR + is approximately ~20 days or so and average duration of culture positivity (i.e. best proxy for infectiousness) only 4-7 days average. So, ~70% or so of the time you are PCR positive you are EXPECTED to be Ag test negative.
7/x
7/x
This cannot be overstated
A public health test for contagiousness does NOT want to detect ppl after no longer infectious
PCR is simply NOT the right gold-standard... *IF* used as a comparator, the Cts must be interpreted correctly
The BMJ reports by Deeks are simply wrong here
A public health test for contagiousness does NOT want to detect ppl after no longer infectious
PCR is simply NOT the right gold-standard... *IF* used as a comparator, the Cts must be interpreted correctly
The BMJ reports by Deeks are simply wrong here
Unfortunately, the series of letters by @deeksj, some which use wholly inappropriate extrapolations to contort a warped view of reality, is harming global fight against SARS-CoV-2
All Eyes are on UK experience and @deeksj misinformation campaign is confusing governments.
END
All Eyes are on UK experience and @deeksj misinformation campaign is confusing governments.
END
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