BIO SCI 45 Lecture Notes - Lecture 13: Positive And Negative Predictive Values, Antibody
17 Oct 2016
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Antibody test: does not directly measure the virus, measures whether the body has produced antibodies to the virus. Sensitivity-ability to identify true positives; con rm presence of disease. Speci city-ability to identify true negatives; con rm absence of disease. In order to evaluate the validity of a clinical test a gold standard for diagnosis is required. Gold standards are de nitive and often highly invasive: most people with hiv don"t have symptoms. Trade-offs: high sensitivity may come at the expense of many false positives. Similarly high speci city may come at the expense of many false negatives: which of the two, a false positive or false negative, is more detrimental in regards to hiv testing. Step #1: conduct a less expensive/less invasive test. Step #2: conduct a 2nd test among those who tested. Re-screen positives with a more speci c test (western blot)
