Positive predictive value

Positive Predictive Value

Positive Predictive Value (PPV), pronounced as /ˈpɒzɪtɪv prɪˈdɪktɪv ˈvæljuː/, is a statistical concept widely used in medical testing and diagnostic medicine. The term originated from the field of epidemiology and is used to measure the performance of a diagnostic test or measure.

Etymology

The term "Positive Predictive Value" is derived from the words "positive", "predictive", and "value". "Positive" is from the Latin word "positivus" meaning "settled by agreement, positive" (in Medieval Latin "formally laid down"), "Predictive" is from the Latin word "praedicere" meaning "to foretell, predict, say beforehand", and "Value" is from the Old French word "value" meaning "worth, price, moral worth, standing, reputation".

Definition

Positive Predictive Value is defined as the probability that subjects with a positive screening test truly have the disease. It is calculated by dividing the number of true positive results by the sum of true positive and false positive results.

PPV = True Positives / (True Positives + False Positives)

Related Terms

• Sensitivity (tests): The ability of a test to correctly identify those with the disease.
• Specificity (tests): The ability of a test to correctly identify those without the disease.
• Negative Predictive Value: The probability that subjects with a negative screening test truly do not have the disease.
• Prevalence: The proportion of a population who have a specific characteristic in a given time period.
• False Positive: A test result which incorrectly indicates that a particular condition or attribute is present.

See Also

• Diagnostic Odds Ratio
• Likelihood Ratios in Diagnostic Testing
• Receiver Operating Characteristic

External links

• Medical encyclopedia article on Positive predictive value
• Wikipedia's article - Positive predictive value

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