A screening test checks for diseases or conditions before symptoms appear, in an effort to find diseases early when they may be easier to treat or cure.
Fundamentals of Screening:
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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).
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.
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Negative Predictive Value (NPV) is the likelihood that a person with a negative test result truly does not have the disease.
Evans, I. (Ed.). (2011). Testing treatments: Better research for better healthcare (2. ed). Pinter & Martin. http://www.testingtreatments.org/wp-content/uploads/2012/09/TT_2ndEd_English_17oct2011.pdf