BACTERIA
Based on the information in this video, Meridian Diagnostics Inc. decided to produce an enzyme-linked immunosorbent assay (EIA test kit) to screen for presence of Salmonella heidelberg, so patients who became sickened, could be diagnosed quickly and treated. Patient blood samples could be tested for presence of the S. heidelberg bacteria as opposed to other Genera and species of bacteria.
1. With this information, by constructing a 2-by-2 table, calculate the predictive-value positive and predictive-value negative of the EIA in a hypothetical population of 1,000,000 blood donors. Using a separate 2-by-2 table, calculate PVP and PVN for a population of 1000 ill patients. Assume that the actual prevalence of S. heidelberg among blood donors is 0.04% (0.0004) and that of people who ate Foster’s chicken is 10.0% (0.10).
2. Do you think that the EIA is a good screening test for the hospital? Why or why not?
3. Do you think that the EIA performs well enough to justify using the test outcomes in court cases? Why or why not?
4. If sensitivity and specificity remain constant, what is the relationship of prevalence to predictive-value positive and predictive-value negative?
Given their success with the EIA for S. heidelberg, Meridian Diagnostics decided to perfect their design, and use it to produce an EIA to test for E. coli O157 H7.
5. With this information, by constructing a 2-by-2 table, calculate the predictive-value positive and predictive-value negative of the EIA in a hypothetical population of 500,000 blood donors. Using a separate 2-by-2 table, calculate PVP and PVN for a population of 600 ill patients. Assume that the actual prevalence of E. coli among blood donors is 0.02% (0.0002) and that of people who ate Jack-In-the-Box hamburgers is 15.0% (0.15).
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