Suppose a value of 130 mg/dl or higher was considered positive and the prevalenc
ID: 3042548 • Letter: S
Question
Suppose a value of 130 mg/dl or higher was considered positive and the prevalence of undetected diabetes remained the same as questions 2-3 ( available for refrence below)
How would you predict sensitivity (Se) would be affected by this change? Why?
Guess without calculation!
Sensitivity would be [ Select one] ["increased", "no change", "decreased"] because [ Select one] ["TP", "TN", "FP", "FN"] will decrease
How would you predict Specificity would be affected by this change ? Why?
Guess without calculation!
Specificity would be [ Select ONE] ["decreased", "", "increased", "no change"] because [ Select ONE ] ["TP", "FN", "FP", "TN"] will increase.
Please compare sensitivity and specificity and observe how the number in cell a, b, c, and d is changing when you change the cutoff point from high to low (from 180 mg/dl to 130 mg/dl) .
Sensitivity = TP /(TP + FN) = a/(a+c)
Specificity = TN /(FP + TN) = b/(b+d
question 2 -3 for reference
A group of 10,000 people who were asymptomatic for diabetes were screened for diabetes by a test measuring blood serum sugar content. A value of 180 mg/dl or higher was considered positive. The results were compared with those of a second and definitive test (gold standard) which correctly detected all cases and non-cases. The results were as follows: Definitive Test Negative Totals Positive Positive 34 20 54 Screening Test Negative 116 9830 9946 Totals 150 9850 10000 What is the prevalence of undetected diabetes? (i.e., before screening). 3.4 % O 0.5 % 0 1.0% 1.5 %Explanation / Answer
Sensitivity would be increased because TP would increase .
More value will move from the 116 region to the 34 region
Specificty would be decreased because TN will decrease as more values will move from 9830 region to 20 region.
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