The prevalence of undetected diabetes in a population to be screened is approximately 1.5% and it is assumed that 10000 persons will be screened. The screening test will measure blood serum sugar content. A value of 180 mg% or higher is considered positive. The sensitivity and specificity associated with this screening are 22.9% and 99.8%, respectively.
Set up a fourfold table with appropriate numbers in each cell of the table.
Calculate the following values:
The percentage of false positives
The percentage of false negatives
The predictive value of positive test
The predictive value of negative test
To observe the effect of increasing sensitivity, assume a blood sugar screening level 130 mg%, with a sensitivity of 44% and specificity 99.0%. Calculate the following values when the number of persons screening is 10000 and the prevalence of undetected diabetes is 1.5%:
Calculate the percentage
False positive
False negative
Positive predictive value
Positive predictive value
How many false positives and false negatives will occur if 100000persons are screened
Look at the following table:
Testpopulation
urine
blood
diabetic
Non diabetics
+
-
7
3
-
+
23
11
+
+
45
7
-
-
124
7620
total
199
7641
Calculate the sensitivity and specificity for:
Blood sugar test
Urine sugar test
In parallel, both urine sugar and blood sugar performed
In series, both test were done