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
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.

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.

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.

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.

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)

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.

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
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.

You can follow @michaelmina_lab.
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