CASE 7

21. A recent study has identified a novel compound in the blood that can better predict the risk of stroke. A screening test for this novel compound, X10, was developed and tested in a population of patients who recently had a stroke. After testing it was determined that circulating X10 levels greater than 100 nM indicated a high risk stroke patient. After using the screening test in the general population it was found that this X10 concentration produced too many false-positive results, therefore the screening test value for X10 levels was increased to 500 nM in order to be considered at risk for a

stroke. How would this change affect the PPV and NPV? How would this change affect the sensitivity and specificity?