Sunday, April 05, 2020

EpidemEconomics

Economics is an inextricable part of pretty much every part of life. Epidemics are no different. Most of the focus of it so far has been the dilemma all countries have gone through, that is, the initial weighing up of suppression of the virus versus a temporary loss of economic activity, that has now morphed into the dilemma between mitigating the damage and a world recession. Now, almost all countries have accepted that the disease is worth the damage of the cure and have done steps to hobble themselves to flatten the curve. Just like China did. So we're all in for an interesting time.

The more interesting thing for me is the smaller, more soluble economic issues. Probably the most interesting is that of testing, which any follower of any of this pandemic will know is one of those key parameters which has differentiated countries. The United Kingdom, after not reacting fast enough to the arrival of the virus, decided that there was not much purpose for testing beyond diagnosis in the hospital. The United States decided to refuse the WHO test and develop their own faulty test which delayed them. On the flip side, South Korea and Germany are now the "stars" of testing, pretty much confirming that the secret to good containment is not a secret; it's exactly what the WHO has suggested: test, isolate, contact trace.

But in almost every country there is the cry of people not being tested who should have, and it's fair enough to feel outraged when knowing or not knowing could affect the lives of your loved ones and your professional life. But my administrator brain does not think it is reasonable to expect that any one who wants a test should get a test and the answer is economics.

I'm no expert but testing as it is done to diagnose people for their infection with the virus has several components. One is the test kit, which has swabs for the nose and throat. The next step is exposing that sample to a PCR process, a polymerase chain reaction. This is when the sample is treated with the enzyme, polymerase, which reacts to any RNA in the sample and multiplies it to a huge amount. Then the final stage is when a reagent is added. The reagent is a chemical that is reactive to the RNA to Covid-19. And voila, you should have a result. What's so difficult about that?

Firstly, you need the test kits, which need to be sent to the testing centres in sufficient supply for the need, and to general practices. Then you need to have the capacity and expertise to do the clinical work with the enzyme and the reagent, and you need to have sufficient amounts of these two chemicals.

The smoke and mirrors of this is that testing is not the same as processing a result. In the US, ashamed by their slowness, they ramped up testing, claiming to send a million test kits out in a week. "Anyone who wants a test can get a test," Trump famously said. But that did not make much difference to the situation because there wasn't the capacity to do the clinical tests on the samples. They used private labs but many of these struggled to scale up their services to the scale that a pandemic required. Once samples are sent to a private lab, sometimes there are too many samples for their daily capacity and the backlog of people waiting for results went into days, where presumably people are out of action and isolated, perhaps needlessly.

To ramp up testing you need to have not just the kits but also the laboratory resources, and an administrator thus will be careful to have measures in place to prevent wastage and overuse. Where there are scarce resources there must be management of them and the moderation of the case definition seems to have been the tool for controlling the number of tests.

The ideal of "testing everyone" is unrealistic, but also dangerous. Certain tests are famous for their "false positives". The process above is one that can result in "false negatives". If you test too soon, you might clear someone who is just a day short of having detectable virus in the sample. New Zealand's terminology of "probable" cases I haven't seen elsewhere. I presume this is the apparent case of Covid-19 but with a currently negative result. 

1 comment:

James said...

Just two thoughts to add here:
1) If you can't test everyone, then you need a risk-based approach. Test those people who have been exposed to factors that make them more likely to have the disease (e.g.: they just returned from a holiday to New York).
2) Theory of constraints. To improve a process, you need to locate the bottlenecks and remove them, or at least mitigate them as much as you can. As you imply, there is no point sending out a million testing kits, if there aren't enough expert technicians to administer them.