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Covid-19 test result calculator
How to interpret test results
© 2020 BMJ Publishing Group Ltd.
Interactive
Have
covid-19
Do not
have
covid-19
Test positive
Test negative
Pre-test probability
The likelihood a person
has covid-19 based on
their characteristics
Test sensitivity
The proportion of
patients with covid-19
who have a positive test
Test specificity
The proportion of
patients without covid-19
who have a negative test
They are
appropriately
told to
self-isolate
Are told they do not
need to self-isolate
so they go out and
infect more people
They are told they
need to self-isolate
when they would
be safe to go out
Are told they do not
need to self-isolate
and are safe to
go out
PPV (Positive
predictive value)
NPV (Negative
predictive value)
Probability
of having covid-19
if test is positive
Probability of not
having covid-19
if test is negative
If 100 people were tested with these values
56
19
1
24
98%
44%
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
%
%
%
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