Just as highly important information on antibody testing has started to come in for other states, Governor J.B. Pritzker recently announced that he will de-prioritize that testing. He's withholding results collected so far in Illinois.
It's a mistake and the opposite of what other states are doing.
Antibody tests, also called serology tests, are important because they indicate how much of the population had coronavirus, though they probably never knew, and are therefore likely to be immune for some time. That information is also a key variable heavily influencing projections about rate of future infections.
Many headlines from other states are starting to focus on antibody testing because surprising results are now coming in that may begin to inform their policy on the virus. The tests only became available in early April.
Getting particular attention are new numbers from New York and Florida, where very large parts of the population tested positive for antibodies.
One in five New Yorkers may have had Covid-19, the tests suggest, as reported by the New York Times on Thursday. Governor Andrew Cuomo said that might mean the death rate is far lower than believed.
Miami-Dade County test results also showed a surprisingly big part of the population with antibodies. About 6% – around 165,000 residents – have antibodies, indicating a past infection by the novel coronavirus. That dwarfs the state health department’s tally of about 10,600 cases, according to the Miami Herald on Thursday.
A recent Stanford University antibody study estimates that the fatality rate if infected is likely 0.1 to 0.2 percent, a risk far lower than previous World Health Organization estimates that were 20 to 30 times higher and that motivated isolation policies, as reported by The Hill.
Antibody testing started this month in Illinois with quite a bit of fanfare and publicity. The Chicago Tribune, for example, quoted a spokesman from Family First Medical Group saying, “The test we’re using … is the one most supported by the medical community, including researchers from Stanford…. We’re confident in its safety and results. Overall, they seem to be very accurate.”
What are those Illinois tests saying? That’s what Pritzker isn’t releasing.
But one indication may have come from the Chicago City Wire whose reporters visited Roseland Community Hospital on Chicago’s south side. It was among the first to begin offering serology tests and is doing hundreds of tests per day. A phlebotomy nurse there, according to their story, estimated that a stunning 30% to 50% of patients have been testing positive for antibodies. I emailed the hospital for comment but got no response.
Reliance on antibody testing by individuals has been challenged because the testing has a high error rate, producing many false positives in particular. The Food and Drug Administration has warned about those inaccuracies and said not to use the tests as a “sole” basis for diagnosis of the virus, although it recommends continued use of the tests. Some in Congress, too, are worried about people relying on inaccurate tests. However, some tests may be more accurate than others. Abbott Labs claims its test is 99% accurate. It has been approved for use in the European Union where millions of the tests are now being distributed.
But there’s a critical distinction here between an individual relying on the tests and the broader empirical value of what the tests indicate about general immunity levels. Dr. Scott Gottlieb, the former commissioner of the Food and Drug Administration has said just that. Given the frequency of false positives, nobody should think they are bulletproof if they get a positive test.
However, adjustments to reflect the error rates can be made for broader research purposes, and that’s the key. As stated in that Miami Herald article about the study there, “researchers used statistical methods to account for the limitations of the antibody test, which is known to generate some false positive results. The researchers say they are 95% certain that the true amount of infection lies between 4.4% and 7.9% of the population, with 6% representing the best estimate.”
Axios put it this way: “You can estimate the spread of a virus in a population with a serological survey (a.k.a. serosurvey), even with a less-than-perfect test. Then you can account for false results using statistical techniques in your analysis.”
Why is Pritzker refusing to publish this data? Maybe he thinks it’s his place to take it upon himself to protect individuals from their own misuse of the testing. On the other hand, if results here are consistent with New York, Florida, other states and what those Stanford researchers say, projections would undoubtedly be far rosier and Pritzker’s recent extension of stay-at-home rules would become more controversial. And Pritzker seems unconcerned about distinguishing the tests known to be inaccurate from those who claim to be accurate, such as Abbott Labs’.
I’d like to tell you to decide for yourself about how much to make of the new antibody test results for Illinois; I am not trying to make that call for you. But we can’t decide for ourselves because we don’t have the information. Pritzker won’t release the data and now he will cut back on the testing.
Illinois should be collecting and publishing antibody test results just as other states are.
Scrubbing hands is good. But scrubbing key data isn’t.