1. I'm enthusiastic about the prospect of cheap, fast, at-home paper strip COVID tests for daily proactive screening.

To get the most out of them, we need to start thinking now about issues around incentives and individuals behavior.

2. The first thing to recognize is that, rather like masks, proactive testing is largely about protecting others, not about protecting you. There is little if any therapeutic value to catching your own COVID infection in the pre-symptomatic or asymptomatic phase.
3. The whole point is that a paper strip test acts as a sort of "artificial symptom", allowing you to tell that you are infected, and take the necessary steps to isolate yourself and avoid spreading infection to others.
4. At the same time, proactive testing carries individual costs: those associated with purchasing the tests, time costs of taking them, and serious social and economic costs if one tests positive and has to self-isolate for upward of a week.
5. So, we have an intervention that is costly to you but beneficial to others. We need to think about what the incentives are for people to (1) decide to take a daily test before the results are known and (2) follow through appropriately if a test comes up positive.
6. In the language of economics, proactive testing is individually costly but generates positive externalities: benefits to others that are not priced into any market exchange for the good or service at hand.
7. In general, public choice theory suggests that some sort of higher-level intervention (usually governmental) is necessary to bring about socially optimal outcomes in these situations. I've written about this previously in a public health context: pnas.org/content/early/…
8. For starters, the tests have to be subsidized—and in this case, I think made freely available. This isn't enough, though. Even if the tests are free, what it's in for me for using one every day, and risk having to miss school, work, social events, etc. should I test positive?
9. Some people will do this out of the goodness of their hearts, the same way that people donate blood or even bone marrow.

But that will only get us so far.

Some people won't want to, and others simply won't be able to afford to because of the financial realities..
10. If we want people to test themselves and then self-isolate, we have to make it financially feasible. People who test positive (presumably w/ some sort of lab verification) will have be paid a living salary while self-isolating.
11. If we don't do this, not only will uptake be lower, but testing and self-isolation to protect family and community will be a luxury reserved for the wealthier Americans, further exacerbating health inequalities in this country.
12. @ay_zhou and others have pointed out to me that there's an important strategic difference between at-home paper strip tests and even saliva tests that one sends in to a lab. Namely, with the paper strip test I get to choose whether I want to report a positive result.
13. With lab-read tests, the lab (and thus the public health system) knows the result before I do. This makes a difference; I might be well-meaning in agreeing to take a test, but change my mind about reporting and isolating once a positive result obtains.
14. I think that this is a concern that merits consideration.

There are plenty of things that we agree to do, assuming they'll come at no real cost, but would back out of if we could when those assumptions prove wrong.
15. (Academia is almost entirely driven by this fallacy coupled with an inability to adequately weight the future. I frequently agree to give talks and review papers in the distant future—but seldom, when it's time to follow through on my promise, would I not welcome an out.)
16. In summary, we need to (1) recognize that the benefits to widespread proactive testing are positive externalities and recognize the need for mechanisms to support production of those externalities, (2) think hard about how we are going to ameliorate the costs of being tested,
17. And (3) recognize that at-home self testing offers an additional opportunity for the patient to back out of the process once the result is known and think about ways to deal with this.The sooner we start addressing those implementation details, the better the rollout will go.
18. Finally, disclosures: I have a paid consulting relationship with Color Genomics, but no financial interest in the production or sales of COVID tests or treatments.
19. I do have vested interests in going places, seeing people, working at work, eating at restaurants, drinking at the bar, playing sports, hearing live music, sending my kids to school, visiting other countries, and photographing birds that can’t be bothered to visit Seattle.

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