Quick Thoughts on Our First Sampling Run

post by jefftk (jkaufman) · 2024-05-23T00:20:02.050Z · LW · GW · 3 comments

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Cross-posted from my NAO Notebook

While the NAO has primarily focused on wastewater, we're now spinning up a swab sampling effort. The idea is to go to busy public places, ask people to swab their noses, pool the swabs, sequence them, and look for novel pathogens. We did our first collection run yesterday:

After months of planning and getting approvals, it was great to be out there! Some thoughts on how it went:

• In two hours in Kendall Square we collected 27 swabs, or 13.5/hr. I think with some optimization (below) we could do about ten times this rate.

• It was very bursty. Mostly people ignored us, I think because they thought we were asking for money. When someone did stop to provide a sample, and especially when multiple people stopped, they dynamic changed dramatically. The crowd did the advertising for us, and we had people giving us samples as fast as we could collect them. Most of our samples came in a small number of bursts.

• This means we need to be sampling at a location and time when there's enough foot traffic that we can maintain a crowd: bringing in each new person while the previous one is still providing a sample. (This is very familiar from busking.)

• Mid-morning in Kendall Square was not this: we were sampling at the time that was convenient for us, which was too late for most of the morning commuters and too early for people out getting lunch. I suspect 8am-9am, 12-1pm, and 5pm-6pm would have been much better times.

• There are also higher foot traffic areas around Boston than Kendall Square: we only started in Galaxy Park because that was, again, convenient for us. In this case, however, convenience matters enough that for our initial few iterations I think we'll stick to Kendall.

• When you don't have a crowd yet, it's really valuable for people to be able to tell whether they want to participate from reading the sign. I think Simon did a great job making a professional-looking sign, but the text describing the core of what we're asking ("swab your nose, get $5") is too small. For our next collection run we'll print a new banner with the title and subtitle swapped.

• The banner is only readable from one side, but people don't only come from one direction. The traditional approach is to wear a sandwich board, but this doesn't seem very professional. I'm thinking maybe two of these retractable banners, back to back?

• We're having people swab their noses and then seal the swab in a vial before dropping it into a box. I think it's pretty likely that once we have more experience at this we can work out a system where we can safely put the swabs directly in the box, though this will require coordinating with our biosafety officer. This would be cheaper (no vials) and simpler for participants (no recapping).

• We're initially testing offering $5/sample. This is a tradeoff between spending money on compensation to get more participants per hours, and having staff paid to be out there for more hours. I think once we have the rest of the operation working well (sampling in good places and times, good crowd interaction, good signage) we'll be able to get good results with less compensation ($1, $2, candy bar, granola bar, etc). But since I think we'll learn faster if compensating at the higher rate because we'll have more people to sample from, I don't think we should start optimizing that area yet.

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