<prompt> Due to an effective prevention program, the pre valence of an infectious disease in a community has been reduced by 90. A physician continues to use the same diagnostic test for the disease that she has always used. How have the tests characteristics changed?Its sensitivity has increasedIts positive predictive value has increasedThe tests characteristics have not changedIts negative predictive value has increased  <response>: PPV and NPV of a screening test depends on: Sensitivity Specificity Prevalence of disease in the populationIn this question, since a physician continues to use the same diagnostic test for the disease that she has always used, sensitivity and specificity of the test will remain sameBut predictive value of a test PPV and NPV depends on prevalence of a disease in a populationPPV is directly proportional to prevalence of disease in the population PPV á Prevalence of disease As the prevalence of a disease increases in a population, PPV increases for the screening testNPV is inversely proportional to Prevalence of disease in a population NPV α 1 Prevalence of disease As the prevalence of a disease increases in a population, NPV decreases for the screening testTherefore, since the prevalence of an infectious disease in a community has been reduced by 90, its PPV will reduce and its NPV will increase 