The positive predictive value of a screening or diagnostic test indicates the likelihood that a person with a positive test result would actually have the condition for which the test is used; i.e. the probability that a positive test result is correct.
The higher the value of the positive predictive value (for example, 90% would be considered a high value), the more useful the test is for predicting that the person has the condition.
For example, the positive predictive value of mammography in breast cancer screening has been estimated to be less than 30%. That means that for every 100 people who have something discovered on their mammogram that looks like cancer, it will turn out actually to be cancer in less than 30 of those people.
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