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Covid-19 antibody tests
Calculator for interpreting test results
© 2020 BMJ Publishing Group Ltd.
Interactive
Pre-test probability
Likelihood had covid-19
based on symptoms and
background rates
Test sensitivity
Proportion of people who
have had covid-19 with a
positive test
Test specificity
Proportion of people who
have not had covid-19
with a negative test
If 1000 people were tested with these values
True positive
False positive
False negative
True negative
Antibody
test
positive
Antibody
test
negative
May provide relief or reassurance. Risk that
they could assume they are immune
No change to management or behaviour.
Might improve adherence to social distancing
Unlikely to change clinical management
or behaviour
Risk of false reassurance, could assume that
they are immune and change behaviour
Probability
has had
covid-19
if test is
positive
Probability
has had
covid-19
if test is
negative
56
19
1
24
98%
56%
people who test
positive have covid-19
people who test negative
have covid-19
person who tests positive
does not have covid-19
people who test negative
do not have covid-19
Adjust these values to
update graphic below
%
%
%
have had covid-19
800
have not had covid-19
200
Please enter a number
between 0 and 100
Please enter a number
between 0 and 100
Please enter a number
between 0 and 100
DRAFT