City not counting some COVID-19 cases
Positive antigen results omitted if asymptomatic
Even as the city begins to reopen parks and playgrounds, the San Antonio Metropolitanhealth District is not counting some patients who test positive for the novel coronavirus or starting an investigation to trace their contacts.
If a person has no symptoms of COVID-19 but tests positive for the virus in an antigen test, Metro Health does not count the result as a case or start a public health investigation to track down people they may have exposed, city officials confirmed.
The gap raised alarms this week among members of a Metro Health contact tracing work group concerned the practice could downplay the prevalence of the disease in the community and contribute to further spread of the virus. Those worries were dismissed by Metrohealth’s director as “a whole lot of ado about nothing.”
Positive results from antigen tests are highly accurate. Most antigen tests correctly identify the virus more than 99 percent of the time, according to the Centers for Disease Control and Prevention. And they’re rapid; the tests can identify infectionswithinminutesby detecting proteins from the virus in secretions from the nose and throat.
Even people without symptoms can transmit the virus. Experts say about 40 percent of infected people have no symptoms.
Yet, Metro Health instructed case investigators this week to classify people with positive antigen test results but who don’t have symptoms as “not a case.”
“DO NOT assume antigen positive individuals are asymptomatic,” the instructions read, emphasisbymetro Health. “If person is determinedtobeasymptomatic from a phone call: Kindly inform person that they are not considered a case by the city of San Antonio.”
Investigators are then instructed to close the case without starting a public health investigation.
Thereason, saidassistant
Citymanager andmetrohealth Director Colleen Bridger, is that the Food anddrug Administration has authorized the use of antigen tests only in people who have symptoms of COVID-19.
“Right now, they're saying that there isn't enough evidence for them to approve the antigen test for people who do not have symptoms,” Bridger said.
Outside of congregate settings such as nursing homes, the number of asymptomatic cases in Bexar County has been “exceedingly low” — less than 1,000 people, Bridger said. She noted that by contrast, Metro Health has reported and traced 9,786 antigen positive patients with symptoms.
Bexar County has had a total of 53,794 cases since the pandemic began earlier this year.
FDA spokesman Jim Mckinney said the agency authorizes tests to be used only in ways for which a company's data demonstrates the test is accurate. He said the FDA has authorized the use of antigen tests only for patients who are within five days of the onset of symptoms.
But “the reason these limitations are here,” Mckinney added, “is the risk of potentially missing cases” — not the risk of falsely detecting positive cases.
Antigen tests are not as sensitive as PCR tests, so a negative result from an antigen test does not rule out an infection. Negative results from an antigen test may need to be confirmed with a PCR test, which looks for pieces of the virus in the nose or throat.
A positive antigen test, however,
means the person likely has an active COVID-19 infection.
For that reason, anyone who tested positive in an antigen test should be counted and traced, said Dr. Joseph Petrosino, chairman of the Department of Molecular Virology and Microbiology at the Baylor College of Medicine in Houston.
Metro Health's policy is “a general practice by most health departments, by what I've understood,” Petrosino said. “You can understand where the health department is coming from. However, these (antigen) tests are typically associated with a high accuracy in terms of positive sensitivity.”
Unlike some other cities in Texas, Metrohealth does include antigen positive patients with symptoms in its total COVID-19 case count, classifying them as “probable.” But the FDA limitations prevent the city from including antigen
positive patients without symptoms even as “probable,” Bridger said.
Petrosino said health departmentsdohave the autonomy to account for such cases.
“I understand the letter of the law and all that kind of stuff, and who knowswhat the political pressures are depending onwhere you are, but at the very least you could account for them in a separate category,” Petrosino said. “Counting is important enough because your disease prevalence in the community is what dictates public policy on reopenings. If they're not even following up on positive antigen cases, then what's the point?”
Both Petrosino and Mckinney noted that the FDA allows health care providers to use tests “off-label” for people without symptoms, “even if (the tests) are not specifically authorized for this indication,” according to recent FDA guidance.
On Wednesday, Chris Van Deusen, spokesman for the Texas Department of State Health Services, said “the science and recommendations” aboutcovid-19 are rapidly evolving.
“People who test positive with an Fda-authorized antigen test should be treated as likely having a COVID-19 infection and followed up on per the local health department's practices,” he said.
Back in July, city officials defended their counting of antigen positive patients with symptoms by stressing the accuracy of positive results from the test.
“Antigen tests are Fda-approved, and positive tests are highly accurate,” Bridger said then in a statement.
Dr. Junda Woo, Metro Health's chief medical officer, echoed this at a briefing.
“These are people who really do have COVID,” Woo said.
Mayor Ron Nirenberg concurred at the time.
“Those people HAVECOVID, and they should be counted,” themayor said.
This week, members of a Metro Health contact tracingwork group emailed city officials to ask why the city is not counting and tracing everyone who tests positive by an antigen test.
One member, Courtney Denton, noted that thecouncil of State and Territorial Epidemiologists updated its classification last month so that “there is no scenario inwhich a positive antigen respiratory specimen is not counted as a probable case.”
Denton added, “Bexar County and City of San Antonio should determine if the report to the public will use the most recent version of
CSTE case definitions or provide an undercount that excludes asymptomatic antigen cases.”
Robert Huesca, another member of the group who works as a case investigator, recommended that case investigators “complete full (Texas Health Trace) interviews with asymptomatic cases.”
Cherise Rohr-allegrini, an epidemiologist who is a member of the work group, forwarded to officials a recent Texas Department of State Health Services document that said: “A positive antigen test means that the person being tested has an active COVID-19 infection. … If positive, the health department will interview the antigen-positive person about symptoms and if they were around someone who had COVID-19. Contact tracing will be performed.”
In the email to city officials, Rohr-allegrini wrote, “Community members and private physicians have been asking questions about why they or their patients are being told not to isolate or that they're not a case when all state and federal guidance says otherwise. I have already gotten calls from the media asking to explain the science behind antigen testing and why it wouldn't be valid.
“As requestedby city leadership I am not speaking to the media at all, instead referring them to (Metro Health) or DSHS for questions.”
On Tuesday, Bridger dismissed the concerns of the work group.
“This just feels like awhole lot of ado about nothing right now,” she said. “I think that they do not have the full understanding of the situation, which is not surprising given they don't currently work in a health department.”