Negative Predictive Value (NPV)

NPV answers the question, ‘If the test result is negative, what is the chance that the person actually does not have the disease?’, and is given by the formula:

Substituting, we get

Interpretation: If a person obtains a negative test result on the ‘Standard Q COVID-19 Ag detection kit’, and the prevalence of COVID-19 in the population is 25% , then the chance that the person actually does not have COVID-19 is 85.59%.