Psychiatric-Mental Health Nurse Practitioner Exam

What does specificity measure in a screening test?

1. The accuracy of identifying disease presence

2. The proportion of the population affected by a disease

3. The rate of true negatives in individuals without a disease

4. The frequency of new cases of a disease

The correct answer is: The rate of true negatives in individuals without a disease

Specificity in the context of a screening test measures the ability of the test to correctly identify individuals who do not have the disease, which is quantified as the rate of true negatives. This means that the higher the specificity, the greater the proportion of those without the disease that the test is able to correctly identify, thus minimizing the number of false positives. This is crucial for ensuring that individuals who do not have the disease are not erroneously classified as having it, which could lead to unnecessary anxiety, further testing, or treatment. In this context, accuracy in identifying disease presence pertains more to sensitivity rather than specificity, as sensitivity measures the ability to identify true positives. The proportion of the population affected by a disease relates to prevalence, not specificity, while the frequency of new cases refers to incidence, which is also distinct from what specificity measures.