NBME 1 ;The genetic disease institute - khushigrover

[ArchivalUser]

40. The genetic disease institute at a university hospital has developed a rapid screening test for a serious but treatable inherited metabolic disorder. Although this disorder is predominantly found in a particular ethnic group, it is also found sporadically throughout the entire population. The screening test has a sensitivity of 95% and a specificity of 90%. When used in an ethnically prescreened population where the prevalence of this disorder is 30%, the positive predictive value is 80% and the negative predictive value is 96%. The institute proposes to use this screening test on the general population where the prevalence of this disease is 0.1%. Which of the following is the most likely result of this screening program?

A
) Negative predictive value decreases

B
) Positive predictive value decreases

C
) Sensitivity decreases

D
) Specificity decreases

[ArchivalUser]

B... sensitivity and specificity are independent of prevalence and raisinng cut off value decreases PPV and increases NPV

[ArchivalUser]

but in the second population.....prevalance is decreased to 0.1%...
can u plz explain what do u mean by raising the cut off value ...........