Step I Tags:False positives

[Fewa Fibroblast]

In a PPD testing if the number of False positives increases what happens to sensitivity and specificity of test?
a. Sensitivity and specificity both decrease
b. Sensitivity increases and specificity decreases
c. Sensitivity and specificity both increase
d. Sensitivity no change and specificity decreases

 

[iBS1972]

This is a key concept, and this is a very typical question and will most likely show up on your step 1 and 2CK. It would be more beneficial for you to first mention what you think the answer is and why, then we can see if your reasoning is correct or where your reasoning is off if you were wrong.

 

[Fewa Fibroblast]

If we lower the cutoff value of diagnostic test then False positive will increase, sensitivity will increase and specificity will decrease. I applied the same concept in this question and got confused. But it says sensitivity doesnot change and specificity decreases. Maybe false positive has no effect in sensitvity and false negative has no effect on specificity.
I think i overthought the question and should have looked at their formulas.

 

[iBS1972]

If we lower the cutoff value of diagnostic test then False positive will increase, sensitivity will increase and specificity will decrease. I applied the same concept in this question and got confused. But it says sensitivity doesnot change and specificity decreases. Maybe false positive has no effect in sensitvity and false negative has no effect on specificity.
I think i overthought the question and should have looked at their formulas.

Great job, your answer and reasoning are perfect