NY antibody test results will give us clues about our future health risks…

 … and may either vindicate or indict the shut-down.
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Last week, Gov. Cuomo announced that New York will begin the “most aggressive” antibody testing in the country this week.

The goal: To determine the true number of people who have been infected by the coronavirus.

Specifically, NY will administer around 14,000 tests this week to a random sample of individuals.

That’s a good thing.

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Teaching point: I always coached my students to develop hypotheses before doing analyses or launching a test.

In high uncertainty situations — like the coronavirus infection rate — I nudged them to imagine the high & low results that might be reasonably possible … and, pre-assess the implications at each extreme.

Let’s play that game for NY’s antibody testing…

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The antibody tests should give us an estimate re: what percentage of the New Yorkers have already been infected with the coronavirus.

If the sample is really random, it should include:

  1. People who were not infected (yet)
  2. Severely symptomatic infected people who were tested (and maybe hospitalized) … these are the “confirmed cases”
  3. Mildly symptomatic infected people who were not tested
  4. Asymptomatic infected people who were not tested.

Group 2 are the infected symptomatics who were tested.  They are a known commodity — the “confirmed cases”.

Groups 3 & 4  are the infected asymptomatics and mildly symptomatics.  They are the wildcards — the main reason that this testing is being done

Note: While the primary goal of this study is descriptive surveillance (i.e. to estimate the percentage of the population that has already been infected), a secondary reason for doing an antibody test is to identify infected people who might be nudged to donate some of their antibody-rich plasma.

OK, so what are our high and low “priors” (i.e. our best guesses before the study is done).

We do have a couple of facts to work with … we know New York’s:

  • Confirmed cases …….… 250,000
  • C-19 deaths to date …. 17,500
  • NY’s Population …….…. 19.5 million

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Low-side estimate

We also have some estimates from other countries re: how the virus effects infected people:

  • 15% severe symptoms
  • 35% mild symptoms
  • 50% asymptomatic

Let’s connect a couple of dots…

The confirmed cases (250,000) and the severe symptoms (15% of all infected) are a reasonably close definitional match.  That is, they should be the same people.

Combining those numbers and doing the arithmetic, suggests that the total number of already infected people in New York is 1.67 million (250,000 confirmed cases divided by 15%) … which is 8.6% of the NY population (1.67 divided by 19.5).

So, we’d expect — on the low-side —  that roughly 1,200 of the 14,000 people being sampled will test positive for the coronavirus antibodies (8.6% times 14,000).

What about a high-side estimate?

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High-side estimate

According to news sources including Palo Alto Online

A Stanford research team recently completed “the first large-scale community-based prevalence study in a major U.S. county — Santa Clara, California”.

Their conclusion: “the number of infections is much greater than the reported number of cases.”

How much higher?

“The number of coronavirus infections in Santa Clara County could be between 50 and 80 times higher than the officially confirmed case count”

Whoa, Nellie … between 50 and 80 times!

Let’s be a bit conservative and use the low estimate: 50 times the officially confirmed case count.

NY has 250,000 confirmed cases.

250,000 times 50 is a whopping 12.5 million … which would be 64% of NY State’s population.

Note: I’ve heard some pundits guesstimate a 70% infection rate.

So, if the Santa Clara study is to be believed,  then about 9,000 (64%) of the 14,000 NY sample should test positive for the antibodies.

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Let’s recap: On the low side, the NY sample (14,000) might have 1,200 (8.6%) testing positive for the antibodies.

On the high-side, there might be 9,000 (64%) testing positive.

So what?

Here’s where things get interesting …

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Low-side implications

If the results are on the low-side, say 10% test positive for the antibodies, then …

90% of the NY population hasn’t been infected yet.

So, either the coronavirus isn’t as contagious as the experts say (an unlikely scenario) … or the stay-at-home program worked to delay the spread of the virus.

But, it means that a lot of infections are still to come when the mitigation policies are relaxed.

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High side implications

If the results are on the high-side, say 65% testing positive for the antibodies, then…

It means that a sizable chunk of the population has already been infected with the virus (with mild or no symptoms).

So, relatively few people are still susceptible to the virus … and enough people have been infected, to form the base for a “herd immunity” that slows the spread to the heretofore uninfected.

That’s very good news.

Any bad news in there?

Yep.

A high-side result would indicate that the mitigation strategy had practically no effect (since the virus spread across a large portion of the population) … and, the damage done by shutting down the economy was unnecessary.

Bottom line:  A high-side would be good news (for us) going forward … and, would be very bad news for the scientists who pushed for the shut-down and for every policy-maker who bought in and implemented it.

So, if there is a high-side result, expect the scientific-political community to impugn the quality of the antibody tests.  Drs. Fauci and Birx have already laid the groundwork for this.

Fauci has been saying that the antibody tests are “unvalidated” (i.e. likely to be wrong).

When Birx was asked about the Santa Clara study in the daily press conference, she answered that the antibody tests are notorious for generating false positives.

This could get very interesting…

 

 

2 Responses to “NY antibody test results will give us clues about our future health risks…”

  1. NY antibody test results… | The Homa Files Says:

    […] See NY antibody test results will give us clues about our future health risks […]

  2. More about NY’s antibody test results… | The Homa Files Says:

    […] start by flashing back to what we said before the test results came […]

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