Epi practicals - 12 April 2021
Epi practicals
12 April 2021
Is this test useful
Practical - HIV
- Q1
| With disease | Without disease | |
|---|---|---|
| test positive | 152 | 20 |
| test negative | 8 | 980 |
- Q2
- Sensitivity=[math]\displaystyle{ \frac{152}{160} = 0.95 }[/math]
- Specificity=[math]\displaystyle{ \frac{980}{1000} = 0.98 }[/math]
- Q3
a)
| With disease | Without disease | sum | |
|---|---|---|---|
| test positive | 38 | 1999.2 | 2037.2 |
| test negative | 2 | 97960.8 | 97962.8 |
| sum | 40 | 99,960 | 100,000 |
- Positive predictive value=[math]\displaystyle{ \frac{38}{38+1999.2}=0.0187 }[/math]
- Negative predictive value=[math]\displaystyle{ \frac{97960.8}{2+97960.8}=0.999 }[/math]
b)
| With disease | Without disease | |
|---|---|---|
| test positive | 316.35 | 13.34 |
| test negative | 16.65 | 653.66 |
| sum | 333 | 667 |
- Positive predictive value=[math]\displaystyle{ \frac{316.35}{316.35+13.34}=0.959 }[/math]
- Negative predictive value=[math]\displaystyle{ \frac{653.66}{16.65+653.66}=0.975 }[/math]
- Q4
To have high sensitivity is more important, because testing blood donor is a screening test and false-negative has to be excluded as much as possible.
- Q5
We need to calculate PPV and show the director how much false-positive donors arise.
- Q6
We should advise the director that donors should be informed to proceed to an additional confirmation test, not just be informed simple positive result.
