7+ Year Member
Nov 26, 2013
Status (Visible)
  1. Medical Student
A 67 yr old woman comes to the physician for a health maintenance examination. Her brother and mother have a history of colon cancer. The physician recommends colonoscopy, but the patient says that she would prefer only for her stool to be tested for blood. The physician explains that testing the stool for occult blood is not appropriate in this case. The physician is most likely concerned about which of the following regarding this test?

A. Low sensitivity
B. Low specificity
C. Potential for a false-positive result
D. Uncertain negative predictive value
E. Uncertain positive predictive value

I want to say A. Anyone has an idea? Why not D?


7+ Year Member
Aug 2, 2011
Status (Visible)
  1. Medical Student
I think the answer may have been B, low specificity, since occult blood doesn't necessarily mean cancer. This question was definitely discussed in the thread for that NBME, try a google search to get the page.


Blood-and-thunder appearance
7+ Year Member
Oct 20, 2012
Up on the Hydra's back
Status (Visible)
  1. Resident [Any Field]
Yeah, I remember this question. Look in the appropriate NBME thread.

I'm pretty sure it's A though, because the goal here is to screen for + rule out colon cancer -- therefore, high sensitivity is necessary. A fecal occult blood can be negative and you can still have colon cancer. A colonoscopy is far more unlikely to be false negative.

D doesn't make sense because there's nothing uncertain about the predictive values of these tests. I haven't personally checked, but I'm sure there are plenty of studies identifying the reliability of the two tests in terms of predictive values and other metrics.
  • Like
Reactions: 1 users
This thread is more than 6 years old.

Your message may be considered spam for the following reasons:

  1. Your new thread title is very short, and likely is unhelpful.
  2. Your reply is very short and likely does not add anything to the thread.
  3. Your reply is very long and likely does not add anything to the thread.
  4. It is very likely that it does not need any further discussion and thus bumping it serves no purpose.
  5. Your message is mostly quotes or spoilers.
  6. Your reply has occurred very quickly after a previous reply and likely does not add anything to the thread.
  7. This thread is locked.
About the Ads