DrVirgo
Forum Hero
Topics: 1042
Posts: 3,344
|
5. The prevalence of TB in one inner city community was estimated to be as high as 10%. To control the spread of the disease, the local public health department is debating instituting a community-wide screeningn program. Although the test they are plannning to use in inferior to the most commonly used tuberculossis screening test, it has the advantage of being cost effective. In preliminary trials, the new screening test was found to have a sensitivity of 70 % and a specificity of 90%. Based on this information, the physician should recommend that the new screening test should not be used because the new test:
A. has a NPV < 50%
B. has a PPV < 50%
C. is accurate <50% of the time
D. is < 50% reliable
E. is subject to selection bias
Will post correct answer later.
Please explain and discuss... Thanks. 
___________________
Our greatest glory is not in never falling, but in rising every time we fall.
|
| DrVirgo
Forum Hero
Topics: 1042
Posts: 3,344
|
This is a good question!
Right Answer is B.
Can anyone please explain?
Thanks!
___________________
Our greatest glory is not in never falling, but in rising every time we fall.
|
| DrVirgo
Forum Hero
Topics: 1042
Posts: 3,344
|
Please... Need explanation.
___________________
Our greatest glory is not in never falling, but in rising every time we fall.
|
| dipsite
Forum Newbie
Topics: 1
Posts: 26
|
Answer in my view should be A.
___________________
Destiny is no matter of chance,it is a matter of choice,it is not a thing to be waited for , it is a thing to be achieved.
|
| r_albayunen
Forum Senior
Topics: 0
Posts: 218
|
ill go with b
|
| docnikki
Forum Guru
Topics: 93
Posts: 680
|
I go with A..NPV comes out to be 25% and its less and screening test should have high negative predictive value because we do specific tests on those screened positive so screening test can have many false positives but should not have too many false negatives. plz everyone explain in their own style so that we get the concept behind the quest asked.
|
| NE
Forum Guru
Topics: 53
Posts: 504
|
10% have the disease- Punet square will be like this:
<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />
DISEASE
TEST
+
-
+
T +
7
F +
9
-
F-
3
T -
81
10
90
PPV = T+/T+ + F+ = 7 /16 < 50
NPV= T-/ T- + F -= 81/ 84 > 50
|
| NE
Forum Guru
Topics: 53
Posts: 504
|
i DON'T KNOW WHAT HAPPENED WITH MY TABLE!!!
I will atach it now- my answer is PPV<50
Attached Files:
SQUARE.doc (26 KB, 54 downloads)
|
| oggn
Forum Elite
Topics: 52
Posts: 169
|
Thanks NE Can you explain how to do this calculation taking prevalence into account.
|
| nagi_step1
Forum Newbie
Topics: 2
Posts: 28
|
prevalence = 10% which means 10 out of 100 people are infected.
so 10 people are having disease. but test sensitivity is 70%. so the test will poitive for 7 out of this 10 people. so TP = 7 FN = 3
remaining people are with out disease as per the given prevalence are 90. specificity of test is 90. to get this 81 out of 90 people should be true negative. so TN = 81 and FP = 9
so from the baove values fing ppv and npv,. u will get the answer b
|
|
| |
| | | | | | | | | | |
