This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Sensitivity, Specificity, PPV, NPV, Subject name: Social & Preventive Medicine
Probability that a person out of those tested positive on a screening test has in fact the disease is known as 
Select and explain. 
A. Sensitivity, B. Specificity, C. Positive predictive value, D. Negative predictive value
C: Positive predictive value
Answer: C: Positive predictive value 
Explanation: Sensitivity Ability of test to identify correctly all those who have the disease, that is "true positive". Specificity Ability of test to identify correctly all those who don't have the disease, that is "true negative". Positive predictive value Probability that subjects with a positive screening test truly have the disease. Negative predictive value Probability that subjects with a negative screening test truly don't have the disease. Screening test results by Diagnosis Screening test results Diagnosis Total Positive a (True - positive) b (False-positive) a+b Negative c (False - negative) d (True - negative) c +d Total a+c b+d a+b+c+d Sensitivity = a/(a + c) x 100 Specificity = d/(b+d) x 100 Positive Predictive Value = a/(a + b) x 100 Negative Predictive Value = d/(c + d) x 100