A 2-day-old newborn undergoes routine newborn screening. An abnormal test result for galactosemia is reported. The physician asks the laboratory to share the number of true positives (those testing positive who have the disease) divided by the number of all those with the disease. Measurement of which of the following is being calculated?

a) Confidence interval

b) Positive predictive value

c) Prevalence

d) Sensitivity

e) Specificity