Clinician’s Probability Calculator

This laboratory uses a Covid-19 test approved to test asymptomatic patients; individuals suspected of COVID-19 by their

healthcare provider; symptomatic patients, within the first seven days of the onset of symptoms

This laboratory or the manufacturer established method performance for this Covid-19 method as follows:

Based on testing

known positive samples, and

known negative samples

PPA (sensitivity) is:

with confidence intervals from to

NPA (specificity) is:

with confidence intervals from to

The Positive likelihood ratio is : with confidence intervals from to

Convert Pre-Test to Post-Test Probability of Covid-19

Positive Test
Maximam Positive Test
Minimum Positive Test
Negative Test
Maximum Negative Test
Minimum Negative Test
Pre-test Probability 1.0% 2.0% 3.0% 4.0% 5.0% 10.0% 15.0% 20.0% 25.0% 50.0% 75.0%

Post-test Probability of Covid-19 with Positive Test Result
from low of
to probable
to high of

Post-test Probability of Covid-19 with Negative Test Result
from low of
to probable
to high of

# of True Positive in every 10 Positive results
from low of
to probable
to high of

# of True Negative in every 10 Negative results
from low of
to probable
to high of

# of False Positive in every 10 Positive results
from low of
to probable
to high of

# of False Negative in every 10 Negative results
from low of
to probable
to high of

One in ‘x’ Positive tests is True
from low of
to probable
to high of

One in ‘x’ Negative tests is True
from low of
to probable
to high of

Table

Condition Positive Condition Negetive Total
Positive Outcome
Negetive Outcome
Total

Calculator

Item Value
Z-score 1.96
Sensitivity
Specifity
Z-score sq
Sensitivity Value
(2np+z-score sq-1)
2+(1/n)
4p(n(1-p))+1
2(n+z-score sq)
z-score sq-(2+(1/n))+4p(n(1-p)+1)
sq root
Lower Limit
(2np+z-score+1)
2-(1/n)
4p(n(1-p))-1
z-score sq+(2-(1/n))+4p(n(1-p)-1)
sq root
2(n+z-score sq)
UPPER LIMIT
Specificity Value
(2np+z-score sq-1)
2+(1/n)
4p(n(1-p))+1
2(n+z-score sq)
z-score sq-(2+(1/n))+4p(n(1-p)+1)
sq root
Lower Limit
(2np+z-score+1)
2-(1/n)
4p(n(1-p))-1
z-score sq+(2-(1/n))+4p(n(1-p)-1)
sq root
2(n+z-score sq)
UPPER LIMIT

Calculations

Modeled data

Sensitivity
sensitivity from low of
sensitivity to reported value
sensitivity to high of
Specificity
specificity from low of
specificity to reported value
specificity to high of

Sens/Spec Reported

Modeled data

LR+ =
LR- =
Pre-test odds
Post-test odds Pos Test
Post-test odds Neg Test
sensitivity / (100 – specificity)
(100-sensitivity)/specificity
Pre-test probability/(1-Pre-test probability)
Pre-test odds x LR+
Pre-test odds x LR-

Sens/Spec Low Confidence Limit

LR+ =
LR- =
Pre-test Probability
Pre-test odds
Post-test odds Pos Test
Post-test odds Neg Test

Sens/Spec High Confidence Limit

LR+ =
LR- =
Pre-test Probability
Pre-test odds
Post-test odds Pos Test
Post-test odds Neg Test