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#1
03-09-2012
 USMLE Forums Master Steps History: --- Posts: 1,365 Threads: 648 Thanked 591 Times in 355 Posts Reputation: 601
Specificity Sensitivity Question!

A diagnostic test has a sensitivity of 64% and a specificity of 99%.
Such a test would carry the risk of which kind of problem?
a. High relative risk
b. Low likelihood ratio
c. False negatives
d. False positives
e. Low power

please explain without using the formula of Sn.

#2
03-09-2012
 USMLE Forums Master Steps History: 1+CK+CS Posts: 1,406 Threads: 118 Thanked 647 Times in 409 Posts Reputation: 657

is it C.......?
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#3
03-09-2012
 USMLE Forums Master Steps History: 1+CK+CS+3 Posts: 1,353 Threads: 94 Thanked 877 Times in 507 Posts Reputation: 890

Sensitivity= TP/TP+FN = 64%

Spec= TN/TN+FP = 99%

Idealy you would want the ratio of 10/10+0.1 (which is 99%)

But 10/10+6 (will be around 62%)
this means that there is a high rate of False Negativites
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#4
03-09-2012
 USMLE Forums Master Steps History: 1+CK+CS Posts: 590 Threads: 31 Thanked 1,233 Times in 411 Posts Reputation: 1257
C.

Sensitivity includes, i.e. picks up all the positives.
Specificity excludes, i.e. does not pick up the negatives.

The test in the question has low sensitivity, so it doesn't pick up all the positives and therefore is prone to false negatives.
 The above post was thanked by: abeer (03-11-2012), tyagee (03-09-2012)

 Tags Biostatistics-Epidemiology, Step-1-Questions

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