Screening is the identification if disease or a risk factor in asymptomatic individuals.
Fundamentals of Screening


Sensitivity and specificity describe how accurate a test is.
Sensitivity is a measure of how reliable a test is in identifying the presence of a condition. It measures how often a test will detect the presence of a disease in people who have the disease (true positives).
Specificity is a measure of how often a test will detect the absence of a disease in those who do not have the disease (true negatives).
True Positive, False Positive, True Negative, and False Negative results are used to calculate sensitivity, specificity, and predictive values of diagnostic tests.
True Positive (TP) = positive test result for a person who has the condition
False Positive (FP) = positive test result for a person who does not have the condition
True Negative (TN) = negative test result for a person who does not have the condition
False Negative (FN) = negative test result for a person who has the condition
Predictive value describes the likelihood that a person has or does not have the condition based on the results of the test. The more prevalent the disease, the higher the PPV and the lower the NPV.
Positive Predictive Value (PPV) is the likelihood that a person with a positive test result truly has the disease.
or
Negative Predictive Value (NPV) is the likelihood that a person with a negative test result truly does not have the disease.
or