Biochemical Tests Flashcards
When would a test show a false negative?
When a person who has the disease has a result that is healthy.
When would a test show a false positive?
When a person who does not have the disease has a result that is unhealthy.
What is the reference interval?
The range of values for a physiological measurement in healthy people.
What is specificity defined as?
Percentage of healthy people who have a normal (negative test).
What is the positive predictive value of a test?
The likelihood of disease in people with a positive test result.
What is the negative predictive value of a test?
The likelihood of health in someone with a negative test result.
What is prevalence also known as?
The pre-test probability of disease.
What is prevalence?
The percentage of total people tested who have the condition.
How can the prevalence change?
If you test a different group of people with more/less risk of disease.
How does a decrease in prevalence affect the PPV and NPV?
PPV falls, NPV rises.
How does prevalence affect sensitivity and specificity?
It doesn’t.
How can the diagnostic cut off affect the specificity and sensitivity of a test?
Increasing the diagnostic cut off increases the specificity and decreases the sensitivity and vice versa.
