Question
Glaucoma is an eye disorder characterized by increased intraocular pressure and visual field defects. Glaucoma can be diagnosed with a gold standard test, but it would be less expensive to screen for glaucoma by assessing intraocular pressure. In one assessment of a new intraocular pressure test and glaucoma, anyone with intraocular pressure more than 21 mm Hg was classified as screening positive for glaucoma. The following is a 2 x 2 table for glaucoma using the gold standard and the new intraocular pressure test among 1,213 individuals.
Disease (Glaucoma)
| ||||
Test
Intraocular Pressure
|
+
|
-
|
Total
| |
+
|
414
|
219
|
633
| |
-
|
0
|
580
|
580
| |
Total
|
414
|
799
|
1,213
| |
A. What is the sensitivity and specificity of the new test? Interpret these values.
B. In the following 2 x 2 table, a new cut point of 25 mm Hg was created to indicate glaucoma. Calculate and interpret the sensitivity, specificity, NPV, PPV of this test with the new cutoff.
Disease (Glaucoma)
| ||||
Test
Intraocular Pressure
|
+
|
-
|
Total
| |
+
|
381
|
3
|
384
| |
-
|
33
|
796
|
829
| |
Total
|
414
|
799
|
1213
| |
Source: 250A Problem Set: Screening & Causality Question 1 Part A and B
