guys neeed helppppppppp on this to understand - lotus2008

[ArchivalUser]

the Elisa test for HIV test has a sensitivity and specificity of 99.9% in a population of 100.000 people where the prevalence of HIv is 1% there will be one false negative and 99 false positive likewise 999 true positive and 9890 true negative
1000hiv+, 999T+, 1T_

99000hiv-, 98901T+, 99T_

if an analysis was made of blood donor pool in which blood has already been screened for hiv and now the prevalance of hiv wasm 0.1%mhow would sensitivity specificity, PPV and NPV change?
dec=decreased
ans
decreased, sensitivity,dec specificity, dec PPV, decNPV
dec sensitivty, dec specificity, same ppv, same npv
same sensiti, same specifi, same ppv, same npv
same sen, same specifi, decppv, decnpv
same sens. same specif, dec ppv, increased npv



guys pl answer and explain

[ArchivalUser]

same sens & specificity (these are characteristics of the actual test, not affected by prevalence). If prevalence is decreased, PPV decreases and NPV increases.