Negative Predictive Value Calculator


Instructions: This Negative Predictive Value Calculator computes the negative predictive value (NPV) of a test, showing all the steps. Please provide the information required to fill out the 2x2 table below with the information about disease presence and absence, and screening test status:

Disease Present
Disease Absent
Test +
Test -

More about this Negative Predictive Value Calculator

The Negative Predictive Value a test (NPV) corresponds to the probability that a patient does not have the disease, given that the patient tests negative.

How do you compute the Negative Predictive Value of a test?

Consider the following 2x2 crosstabulation about the results of the screening test 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 \(TN + FN\) is the total number of those who test negative, the negative predictive value of the test is

\[\text{NPV} = \displaystyle \frac{TN}{TN + FN}\]

What are other related metrics to negative predictive value (NPV)?

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

How to calculate sensitivity and specificity, PPV and NPV using 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.




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