Test Sensitivity Calculator


Instructions: This Sensitivity Calculator computes the sensitivity of a test, showing all the steps. To that end, please fill up the required table with the information about disease presence and absence, and screening test status:

Disease Present
Disease Absent
Test +
Test -

More about this Test Sensitivity Calculator

The sensitivity of a test corresponds to the probability that the test detects correctly people who have the disease.

How do you compute the sensitivity of a test?

Let us consider the following 2x2 crosstabulation about test screening and presence of the disease:

 
Disease Present
Disease Absent
Test +
\(TP\)
\(FP\)
Test -
\(FN\)
\(TN\)

• The value \(TP\) corresponds to the number of true positive cases, which is when the test shows positive for patients with the condition.

• The value \(FP\) corresponds to the number of false positive cases, which is when the test shows positive for patients who don't have the condition.

• The value \(FN\) corresponds to the number of false negative cases, which is when the test shows negative for patients with the condition.

• The value \(TN\) corresponds to the number of true negative cases, which is when the test shows negative for patients who don't have the condition.

Since \(TP + FN\) is the total number of positive cases (people with the condition), the sensitivity of the test is computed as

\[\text{Sensitivity} = \displaystyle \frac{TP}{TP + FN}\]

What are other related metrics to sensitivity?

When working with the characteristics of a test, you probably are going to be interested in knowing about the specificity of the test, the positive predictive value (PPV), as well as the negative predictive value (NPV).

How to calculate sensitivity and specificity in excel

You need to follow the same calculation formula used above to compute the sensitivity and specificity of a test in Excel. First, you need to put the elements in the crosstabulation form specified above.

Make sure to correctly identify the position of \(TP\), \(TN\), \(FP\) and \(FP\), because the result of the calculations WILL depend on the order to the inputs in the table, so make sure to be careful with that.




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