The 4 allele of the gene encodeing apolipprotein E (APOE) is strongly associated
ID: 3152933 • Letter: T
Question
The 4 allele of the gene encodeing apolipprotein E (APOE) is strongly associated with Alzheimer's disease, but its value in making the diagnosis remains uncertain. A study was conducted among 2188 patients who were evaluated at autopsy for Alzheimer's disease by previously established pathological criteria [15]. Patients were also evaluated clinically for the presence of Alzheimer's disease. The data in table 3.14 were presented. Suppose the pathological diagnosis is considered the gold standard for Alzheimer's disease. Question 1: If the clinical diagnosis is considered a screening test for Alzheimer's disease, then what is the sensitivity of this test? Question 2: What is the specificity of this test?
Clinical Dianosis Alzheimers Disease Other Causes of dementia Alzheimer's disease 1643 190 Other causes of dementia 127 228Explanation / Answer
Answer 1: Sensitivity refers to the test's ability to correctly detect patients who do have the condition
Sensitivity = Number of True Positive/(Number of True Positive+Number of False Negative)
Sensitivity = 1643/(1643+190) = 0.896
Answer 2: Specificity relates to the test's ability to correctly detect patients without a condition
Specificity = Number of True Negatives/(Number of True Negative+Number of False Positives)
Specificity = 228/(228+127) = 0.642
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