PBL Sessions: AIDS


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Page 5

Further History:

Celeste has been started on zidovudine therapy.

HIV testing is performed on Mike and Dionne. They are both negative.

The diagnostic sensitivity and specificity of the standard enzyme immunoassay (EIA) initial screening test on patient blood for HIV is illustrated by the following study: In an adult population, 200,000 persons are tested for HIV infection with an EIA test on patient blood for HIV. Of these, 600 are found to test positive by EIA. Of these, 200 are found on subsequent confirmatory Western blot testing to really be infected. Furthermore, follow-up of the original group of patients reveals that there was 1 person who really was infected, but was missed by the initial screening EIA test.

Figure 2: HIV components

Figure 3: HIV - receptor interaction

Tasks

  • Why was Celeste placed on zidovudine?

  • What hypotheses explain the negative HIV tests for Mike and Dionne?

  • Explain your reasoning for the hypotheses you choose.

  • Explain the pathophysiologic mechanisms for HIV infection.

  • Calculate the diagnostic sensitivity and specificity for the EIA screening test for HIV.

    Stop !! Complete discussions and tasks before moving to the next page.