Positive predictive value
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Positive predictive value of a test/investigation is defined as the proportion of patients with positive results being truly diseased.
Positive predictive value = true positives (TP) detected / total positive results
(total positive results = true positive (TP) + false positive (FP)
One can also determine the PPV with an estimate of sensitivity, specificity, and pretest probability (p).
PPV = [(sensitivity) x (p)] / [sensitivity x (p) + (1 - specificity) x (1 - p)]
- unlike sensitivity and specificity, PPV is highly dependent on the prevalence of the disease in the target population
- 1. Parikh R, Mathai A, Parikh S et-al. Understanding and using sensitivity, specificity and predictive values. Indian J Ophthalmol. 2008;56 (1): 45-50. Free text at pubmed - Pubmed citation
- 2. Weinstein S, Obuchowski NA, Lieber ML. Clinical evaluation of diagnostic tests. AJR Am J Roentgenol. 2005;184 (1): 14-9. doi:10.2214/ajr.184.1.01840014 - Pubmed citation