Thread by @NikoEcon

This is an excellent podcast on evidence-based medicine and randomised controlled trials, in the context of Covid-19. W/ @EricTopol & @cuttingforstone hosting @trishgreenhalgh as guest. Implications that I think extend beyond #EBM. A few thoughts. 1/16

medscape.com/viewarticle/98…

@trishgreenhalgh tells about sitting in on a WHO committee discussing the transmission of SARS-CoV2 early on in the pandemic. Scientists who had made their careers on droplet transmission would dismiss the possibility of airborne transmission. 2/n

An evidence-based medicine #EBM approach would require RCT evidence on mode of transmission; or on the effectiveness of interventions such as masking. As @trishgreenhalgh points out, in an emergency with a rapidly spreading pandemic we must be more open-minded -- but to what? 3/n

(1) To interdisciplinary collaboration. The infectious disease specialists should've listened to the aerosol scientists earlier on. A novel emergency is the exact time to recognise that we can all be overly protective of our own turf, and open up our priors a bit (a lot!). 4/n

(2) Open-minded towards observational evidence. RCTs take time to conduct, time which we do not necessarily have in an emergency. Moreover some things -- like community benefits of masking -- are very difficult to study in a (quasi-/)experimental manner. 5/n

Theory can help here. As always when encountering novel emergencies, where decisions must be made before solid evidence is in, one may have to rely on theory.

(In my own field, the #ClimateEmergency is exactly such a problem.) 6/n

These lessons general and apply also in non-medical emergencies. Should we have meta-scientific institutions to promote them -- e.g. an overseeing interdisciplinary panel to promote good practice in expert committees, in whatever field the next emergency comes from? 7/n

Two things I'd like to add. When considering interventions which are not (yet?) supported by gold-standard RCT evidence, but could be seen as reasonable based on a priori theoretical understanding and observational / case study evidence, one needs to weigh costs and benefits. 8/n

That is, put in some economic thinking; keep your priors open and try to aim for a robust policy. What do we know about costs and effectiveness? What do we know about the range of benefits? How bad are worst-case scenarios? 9/n

With masking, costs were likely to be quite small; while potential benefits of reducing the rate of spread of an exponentially spreading novel pathogen can be very valuable. I'd guess a cost-benefit analysis would've recommended masking, before RCT evidence is available. 10/n

In a society-wide emergency, it is not sufficient to rely on medical experts only; interdisciplinary collaboration is absolutely crucial. E.g. Covid-19 has had major macroeconomic impacts & macroeconomic expertise should've been included at the core of scientific advice. 11/n

Of course, one must consider not just the cost of the intervention, but also the effectiveness. Would people really wear the masks? And this brings me to my last point... 12/n

It's become very clear that, in an emergency like Covid-19 was, scientific discussion is conducted under intense scrutiny -- of policymakers, the media, and the public. And scientific disagreements may very easily become fodder for political disagreements. 13/n

Responsible scientists should think very carefully what and how they communicate to the public in such a situation, because what they say in an interview can affect the effectiveness of interventions. 14/n

Masking became politicised very quickly. This will have been fuelled by experts in interviews arguing against masking bc of lack of gold-standard #EBM evidence on benefits. I doubt many such claims were based on any cost-benefit analysis, and if so will have been baseless. 15/n

It is difficult to appreciate the fact that, in an emergency, a prominent field expert actually becomes part of the system they are studying as they affect the behaviour of the population! We should be extremely mindful of how we communicate in such a situation. 16/16