National Public Health Emergency Team (Nphet) official Prof Philip Nolan has admitted that describing the Lidl antigen test as "snake oil" was "not my finest moment in pandemic communication".
Nphet's head of modelling's comments on Twitter last Saturday drew a sharp rebuke from Harvard epidemiologist and immunologist Prof Michael Mina on Sunday.
“For an advisor to your government - you don’t appear to know what you are talking about” with regard to rapid tests, Prof Mina replied to Prof Nolan.
“The comment adds nothing of benefit and further sows confusion. You should be ashamed of your demeanour here.”
In response, Prof Nolan used Twitter to tell Prof Mina that he had “inferred a great deal about my knowledge and motivation from one tweet”.
In a long Twitter thread, Prof Nolan said the criticism of his original tweet was “fair enough”, but he wished to provide a few points of clarification and response.
He said his "snake oil" comment was not a general point about antigen tests, but about the "uncontrolled and unsupported sale of antigen tests by a supermarket chain, and their (one hopes tongue-in-cheek) response to advice from @CMOIreland not to use them, as a negative test might give false reassurance that you are free of infection."
At a Nphet briefing last week the chief medical officer Dr Tony Holohan warned that people might buy sausages, charcoal for the barbecue and a box of antigen tests, to which Lidl Ireland responded: "Weekend Super Savers! Pick up a pound of sausages, charcoal for the BBQ and antigen tests for €31."
Prof Nolan said Ireland had prompt PCR testing so “it is hard to see the value added by self-administered antigen testing”.
He added that Nphet “fundamentally disagreed” with the literature cited by Prof Mina in favour of home antigen tests.
“Fundamentally, we disagree on the recasting of a known limitation of antigen tests (poor sensitivity) as specificity for the infectious state,” he said.
“The claim that antigen tests approach 100 per cennt sensitivity for those who are transmitting (and the infections they miss don’t matter because they don’t transmit) is contested and our interpretation of the evidence differs from yours.
“We are concerned that antigen testing is likely to miss a significant number of infectious cases. This assessment of the evidence is not ‘confused’ or ‘simply wrong’, it is a valid and careful evaluation, and we are not alone in the conclusions we have drawn.
“We do not have great difficulty in differentiating infectious from post-infectious cases with careful public health investigation, and the detection of the latter gives important information in tracking sources and networks of transmission.
“The greater concern is the limitations of antigen tests in detecting the presymptomatic infectious state, and the uncertainty about their actual sensitivity, in the field, in detecting symptomatic infection.
“We are using antigen tests where they add value. They have been used in the management of outbreaks to give early insight into the scale and pattern of the outbreak. They may have value in detecting (re-) emergent disease in high-risk and congregated settings.
“We are looking at a variety of other settings and contexts where antigen testing will be useful, based on international evidence and the outcomes of pilot validation in our own context.”
Prof Mina also stated comments by the Minister for Health Stephen Donnelly criticising antigen tests made him feel "sorry for Ireland".
He added: “It’s about time that they invite someone who actually can explain to them why they are misinterpreting the Cochran review and all of the science behind rapid tests. We’ve written about it extensively. They are simply wrong on this.”