The New York Times - USA (2020-10-26)

THE NEW YORK TIMES, MONDAY, OCTOBER 26, 2020 N A

In the high-stakes world of co-
ronavirus testing, one mistake
has taken center stage: the
dreaded false negative, wherein a
test mistakenly deems an infected
person to be virus-free.
These troublesome results, ex-
perts have said, can deprive a per-
son of treatment and embolden
them to mingle with others, has-
tening the spread of disease.
But false negatives are not the
only errors bedeviling coronavi-
rus diagnostics. False positives,
which incorrectly identify a
healthy person as infected by the
virus, can have serious conse-
quences as well, especially in
places where the virus is scarce.
Although false positives may
seem relatively harmless in com-
parison with their false-negative
cousins, “people can absolutely
get hurt,” said Dr. Benjamin Ma-
zer, a pathologist and diagnostics
expert at Johns Hopkins Univer-
sity.
False positives are generally
very rare among tests that have
been vetted by the Food and Drug
Administration. But any test can
be plagued by contamination,
mishandling or technical glitches,
leading a device to spot the co-
ronavirus where it is not.
Some rapid tests, which forgo
sophisticated laboratory equip-
ment and can deliver results in un-
der an hour, have been criticized
for returning high numbers of
false positives, especially when
used to screen people without
symptoms. Even laboratory tests
that rely on a very reliable tech-
nique called polymerase chain re-
action, or P.C.R., have been known
to return the occasional false pos-
itive.
In places where the virus is rel-
atively scarce, false positives may
even outnumber actual positives
— eroding trust in tests and, un-
der some circumstances, prompt-
ing outbreaks of their own.

Unnecessary Isolation

A positive result on a coronavirus
test sets off a cascade of conse-

quences. According to guidelines

published by the Centers for Dis-

ease Control and Prevention, peo-

ple who test positive should im-

mediately isolate for at least 10

days after their symptoms start

(if they experience symptoms at

all).

That is 10 days spent away from

friends and family, and 10 days of

potential productivity in a school

or workplace lost.

The ever-increasing availabil-

ity of virtual platforms might

make that transition easy for

some, Dr. Mazer said. But for peo-

ple whose work can only be done

in person, or who lack a financial

buffer, “this could be a huge deal,”

he said. “They could lose their

paycheck. They could lose their

job.”

Caregivers, too, may find them-

selves put in a precarious position

by false positives, which could

force them to separate from chil-

dren, older family members or

other vulnerable contacts. Should

another person need to come in

and take their place, the risks of

exposure to the virus could in-

crease for all involved.

And for facilities with limited

space, placing a person in unnec-

essary isolation could shift equip-

ment, medical care and even fol-

low-up tests away from someone

who might need those resources

more.

New Outbreaks

Under certain circumstances, a

false positive could seed new co-

ronavirus cases. Crowded facili-

ties, such as nursing homes, pris-

ons or hospitals, might isolate co-

ronavirus-positive people togeth-

er.

In a worst-case scenario, “if

someone isn’t actually positive,

we could be sending them to their

death,” said Dr. Valerie Fitzhugh,

a pathologist at Rutgers Univer-

sity.

In early October, officials in Ne-

vada ordered the state’s nursing

homes to halt the use of two rapid

coronavirus tests until further no-

tice, citing concerns about accura-

cy. (Nearly 40 percent of the coun-

try’s known Covid-19 deaths have

come from nursing homes, ac-

cording to an analysis by The New

York Times.) A rash of false pos-

itives had been uncovered, ac-

cording to the directive, which had

risked placing uninfected resi-

dents into units with infected peo-

ple, creating a situation that gives

the coronavirus a greater oppor-

tunity to spread. Such a scenario

“could result in causing harm to a

population that we have col-

lectively worked so hard to pro-

tect,” officials noted in a follow-up

directive. Under pressure from

the federal government, Nevada

officials revoked the rapid testing

prohibition on Oct. 9.

Missed or Inappropriate Treatment

False positives can also be disas-

trous from a treatment stand-

point, said Linoj Samuel, a clini-

cal microbiologist at Henry Ford

Health System in Detroit. People

with the flu or Covid-19, for exam-

ple, often show similar symp-

toms, but may only be tested for

one of them at a time. If a patient

is given an incorrect diagnosis of

Covid-19, that person could be de-

prived of treatment that could al-

leviate their illness, or be given a

costly therapy that does little to

speed their recovery.

“That’s definitely a price you

pay,” Dr. Samuel said.

A False Sense of Security

Mounting evidence suggests that

most people who have fought off

the coronavirus once retain a de-

gree of immunity that can thwart

the virus a second time. Scien-

tists do not know how long this

immunity lasts, or how it varies

from person to person, but the

C.D.C. has issued guidelines that

note that reinfection is unlikely

within 90 days. People who don’t

have symptoms within this time

window do not need to be tested

again, the agency has said.

That could be helpful advice for

people who actually contracted

the coronavirus. But people who

unknowingly receive a false pos-

itive on a test might be misled

into thinking that they are invin-

cible, said Saskia Popescu, an in-

fection prevention expert at

George Mason University.

However, if these people never

actually encountered the virus,

they would be just as vulnerable

as before — if not more, should

they choose to forgo masks or

physical distancing after assum-

ing their bodies are already bol-

stered against the virus.

Dr. Catherine O’Neal, an infec-

tious disease specialist at Louisi-

ana State University, expressed

similar concerns when discussing

a false-positive result given to the

University of Alabama football

coach Nick Saban this month.

Should someone be dropped from

routine testing, Dr. O’Neal said,

they would not just imperil their

own health. A false positive could

put an entire group of close con-

tacts at risk.

Undue Stress

With so many of the long-term

consequences of coronavirus in-

fections unknown, a positive re-

sult can understandably take an

emotional toll on the person who

receives it, Dr. Fitzhugh said.

“You hear that news and the first

thing you think is, ‘I could die,’ ”

she said.

On a recent call with Adm.

Brett Giroir, who has led the na-

tion’s testing efforts, Ruth Katz,

senior vice president of policy at

LeadingAge, an association of

nonprofit providers of aging serv-

ices, noted that the repercussions

of false positives had been a

source of extra heartache among

residents and staff members.

Dr. Mazer noted that false pos-

itives on coronavirus tests were

likely to evoke some of the same

stressful reactions as when other

types of clinical screens like

mammograms, which search for

signs of breast cancer, return in-

correct results. “We see the anxi-

ety, the frustration,” he said.

Loss of Trust in Testing

As testing in the United States

continues to increase, experts

have expressed concerns that fre-

quent and high-profile diagnostic

errors could seed disillusionment

among the general public.

Tests with a reputation for spit-

ting out incorrect results of any

kind might struggle to gain wide-

spread traction. People who are

wary of coronavirus tests might

even become more hesitant to

take other types of tests, for fear

that they will not be given the an-

swers they require.

More frequent and accessible

testing is needed — but putting it

in effect could be more challeng-

ing if the public is less willing to

engage, Dr. Mazer said. “That

could have long-term conse-

quences.”

These concerns and more have

prompted several experts to call

for more data evaluating how dif-

ferent types of tests perform out-

side of laboratories and clinics, in

places where most sick people go

to get a diagnosis. Some tests

may be able to effectively screen

the healthy and quash outbreaks

before they spin out control,

while others are ill-suited to for

this purpose. Depending on the

circumstances, certain tests

might need their results to be

confirmed with a second, more

accurate test.

As testing efforts ramp up na-

tionwide, experts said, people

taking tests will need to be well

versed not only in the benefits of

tests but in their limitations as

well.

No test is perfect, Dr. Fitzhugh

said. But tests, and the ways in

which they are deployed, must

still be vetted thoroughly before

they are rolled out in large num-

bers, she said. “People need to

know that the tests they receive

are the best we have to offer.”

DIAGNOSTICS

A False Positive Test Result Can Set Off a Cascade of Other Consequences

Testing for the coronavirus in San Francisco. It may seem harmless, but a false positive test result

can become a source of stress for the person diagnosed, or lead them to a false sense of immunity.

JIM WILSON/THE NEW YORK TIMES

By KATHERINE J. WU

Tracking an OutbreakScience and Research

Other points of view

on the Op-Ed page

seven days a week.

The New York Times

Wordplay, every day.

The New York Times Crossword is the upside to downtime.

It’s the smart way to fill the breaks in your day. Download the app.

nytimes.com/playnow

.