The e4 allele of the gene encoding apolioprotein E (APOE) is strongly associated

Question

The e4 allele of the gene encoding apolioprotein E (APOE) is strongly associated with Alzheimer's disease, but its value in making the diagnosis remain uncertain. A study was conducted among 2188 patients who were evaluated at autopsy for Alzheimer's disease by previous established pathologic criteria. Patients were also evaluated clinically for the presence of Alzheimer's disease. The data in Table 3.15 were presented.

If the clinical diagnosis is considered a screening test for Alzheimer's disease, then what is the sensitivity of this test? Use 3 decimal places in your calculation.

Explanation / Answer

Answer:

Based on the given information:

Clinical Dianosis

Sensitivity of the test (in this case) is the probability that a test will indicate Alzheimer's disease among those with the disease.

Therefore, Sensitivity = A /(A + C) x 100 = [(1643) / (1643 + 127)] x 100 = 164300/1770 = 92.82

So the sensitivity of the clinical diagnostic test is 92.82% Therefore this test will identify ~93% of the patients with Alzheimer's disease.

Alzheimers Disease Other Causes of dementia Alzheimer's disease 1643 ( A - True Positive) 190 (B - False Positive) Other causes of dementia 127(C - False Negative) 228 (D - True Negative)

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