It’s Too Late for Pooled Testing in the United States

I read an exchange on Twitter about pooled testing for COVID-19 and how other countries are using that technique to more quickly identify people who have COVID-19. Unfortunately, we are long past the point where pooled testing would work in the United States.

According to an FDA page on pooled sampling,

Pooling samples involves mixing several samples together in a “batch” or pooled sample, then testing the pooled sample with a diagnostic test. This approach increases the number of individuals that can be tested using the same amount of resources. For example, four samples may be tested together, using only the resources needed for a single test.

Nebraska actually used pooled testing in March, and it was apparently a cost-effective method of quickly testing large numbers of people.

If a pool of 25 samples were to come back negative, all 25 people could be declared infection-free, reducing the overall number of tests by 24. If that pool instead tested positive, a clinic could separate it into smaller pools — five pools of five samples, for instance — and retest. And if, say, two of those smaller pools turned up positive, the clinic could then individually test the remaining 10 samples. Even in the latter scenario, a clinic would save nine of the original 25 tests.

Nebraska eventually gave up on pooled testing for the same reason no one else in the United States is using it–it is only an effective method when the test positivity rate is relatively low.

The person who brought this up on Twitter mentioned its effectiveness in Rwanda, where the test positivity rate is currently at about 1.8 percent.

However, as of December 30, 2020, there is only one state–Hawaii–that has a test positivity rate of under 2 percent. Along with Hawaii, there are only four other states/districts with test positivity rates below 5 percent–Minnesota, Alaska, Washington, DC, and Vermont.

Idaho currently has a test positivity rate of 59.1 percent. California is at 12 percent.

When test positivity rates that high, there’s no point in doing pooled testing because the pooled test is almost always going to come back positive requiring further testing.

This is what happens when your country’s “leaders” count on a virus just disappearing like a miracle rather than make plans and following the science to minimize the impact of a pandemic.

State	New Daily Cases	Tests per 100,000	Test Positivity Rate
Mississippi	1943	59.2	100
Idaho	1514	83	59.1
Alabama	3907	158	40.6
South Dakota	501	105.9	40.4
Pennsylvania	8624	140.6	40.3
Iowa	1661	69.2	36.2
Kansas	391	194.6	28.9
Tennessee	4797	366.2	22
Arkansas	2718	314.9	21.3
Utah	2736	324.2	19.6
Oklahoma	1194	371	17.7
Texas	29535	317	16
Ohio	7526	351.4	15.8
Kentucky	2975	288.1	15.7
Missouri	2941	241.4	15.1
Nevada	1747	411.1	14.8
Arizona	2799	533.2	14.7
Georgia	9450	312.1	14.6
Virginia	4122	331.3	13
West Virginia	528.2	1337	12.1
Montana	427	275.9	12
California	35648	789.7	12
South Carolina	2552	530.2	11.8
Louisiana	3946	366.8	11.3
Indiana	3976	540	11.2
Florida	12075	406	11
North Carolina	3563	463.1	10.4
New Hampshire	1027	484.5	10.2
Wisconsin	2919	423.9	9.1
Nebraska	932	509	8.3
Wyoming	219	458.9	8.3
New Mexico	1216	643.8	8.3
Delaware	701	828.9	8.1
Michigan	3963	355.4	7.7
Illinois	5644	561.1	7.4
New Jersey	3657	632.7	6.9
Maine	0	488	6.9
Massachusetts	4145	955.3	6.5
Colorado	1740	577.2	6.4
Maryland	1878	596	6.2
Rhode Island	1187	1238.2	6.1
New York	10183	935.6	6.1
Connecticut	767	883	5.9
Washington	2174	392	5.8
North Dakota	271	463.6	5.6
Oregon	682	362.3	5.1
Minnesota	972	535.4	4.8
Alaska	183	870.2	3.5
Washington, DC	193	987.6	3.4
Vermon	82	620.1	2.2
Hawaii	71	388	1.9