Predictive value of tests is the
probability
Probability is a branch of mathematics and statistics concerning events and numerical descriptions of how likely they are to occur. The probability of an event is a number between 0 and 1; the larger the probability, the more likely an e ...
of a target condition given by the result of a test,
often in regard to
medical test
A medical test is a medical procedure performed to detect, diagnose, or monitor diseases, disease processes, susceptibility, or to determine a course of treatment. Medical tests such as, physical and visual exams, diagnostic imaging, genetic ...
s.
*In cases where
binary classification
Binary classification is the task of classifying the elements of a set into one of two groups (each called ''class''). Typical binary classification problems include:
* Medical testing to determine if a patient has a certain disease or not;
* Qual ...
can be applied to the test results, such yes versus no, test target (such as a substance, symptom or sign) being present versus absent, or either a
positive or negative test
A medical test is a medical procedure performed to detect, diagnose, or monitor diseases, disease processes, susceptibility, or to determine a course of treatment. Medical tests such as, physical and visual exams, diagnostic imaging, genetic ...
), then each of the two outcomes has a separate predictive value. For example, for positive or negative test, the predictive values are termed
positive predictive value
The positive and negative predictive values (PPV and NPV respectively) are the proportions of positive and negative results in statistics and diagnostic tests that are true positive and true negative results, respectively. The PPV and NPV desc ...
or
negative predictive value
The positive and negative predictive values (PPV and NPV respectively) are the proportions of positive and negative results in statistics and diagnostic tests that are true positive and true negative results, respectively. The PPV and NPV desc ...
, respectively.
*In cases where the test result is of a continuous value, the predictive value generally changes continuously along with the value. For example, for a
pregnancy test
A pregnancy test is used to determine whether a person is Pregnancy, pregnant or not. The two primary methods are testing for the pregnancy hormone (human chorionic gonadotropin (hCG)) in blood or urine using a pregnancy test kit, and scanning ...
that displays the urine concentration of
hCG, the predictive value increases with increasing hCG value.
A
conversion of continuous values into binary values can be performed, such as designating a pregnancy test as "positive" above a certain
cutoff value, but this confers a loss of information and generally results in less accurate predictive values.
See also
*
Positive predictive value
The positive and negative predictive values (PPV and NPV respectively) are the proportions of positive and negative results in statistics and diagnostic tests that are true positive and true negative results, respectively. The PPV and NPV desc ...
*
Negative predictive value
The positive and negative predictive values (PPV and NPV respectively) are the proportions of positive and negative results in statistics and diagnostic tests that are true positive and true negative results, respectively. The PPV and NPV desc ...
References
Medical tests
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