[生物][英文]HIV ELISA 愛滋病 有看沒有懂T_T
(1) The real blood donor pool, which has already been screened for HIV risk factors before they are even allowed to donate blood, so that the HIV sero-prevalence in this population is closer to .1% instead of 1%. How does this change the numbers -- for every 1,000,000 blood donors, 1,000 are HIV positive. Again using a sensitivity of 99.9%, the ELISA would pick up 999 of those thousand, leaving one individual who was HIV sero-positive to slip through the cracks. Of the 999,000 individuals who were not infected, the test would call 998,001 individual sero-negative (true negatives). The ELISA would, however, falsely label 999 individuals as sero-positive (false-positives). Testing the blood donor pool results in as many false positive as true positive results.