The predictive value of a test is a measure (%) of the times that the value (positive or negative) is the true value, i.e. the percent of all positive tests that are true positives is the Positive Predictive Value.
__TP___ X 100 = Predictive Value of a Positive Result (%)
TP + FP
__TN___ X 100 = Predictive Value of Negative Result (%)
FN + TN