The fecal immunochemical test (FIT) is currently the accepted method for early d
ID: 3221712 • Letter: T
Question
The fecal immunochemical test (FIT) is currently the accepted method for early detection of colorectal cancer. It screens for hidden blood in stool from the lower intestines, which is an early sign of colorectal cancer. Those with abnormal FIT results are usually referred for a colonoscopy for a more definitive diagnosis. During the colonoscopy, biopsies can be taken of tissue that seems abnormal. To see whether a repeat FIT screening would reduce the number of unnecessary colonoscopies (which can be perceived as invasive and uncomfortable leading to avoidance), 203 people with abnormal FIT results were given both a second FIT and a colonoscopy. A total of 28 people had biopsies during the colonoscopy that came back with abnormal results and 175 did not have any abnormalities during the colonoscopy. The results of the repeat FIT was abnormal for 22 of the participants with an abnormal biopsy and was abnormal for 13 participants without an abnormal biopsy.
a. Create the 2x2 table
b. Calculate and interpret the sensitivity of this screening test
c. Calculate and interpret the specificity of this screening test
Explanation / Answer
(a)
Following is the 2 x 2 table:
(a)
The sensitivity of this screening test is
sensitivity = 22 /28 = 0.7857 = 78.57%
That is approximately 76% of time results of the repeat FIT give positive results for whom who actually have sign of colorectal cancer.
(c)
The specificity of this screening test is
specificity = 162 /175 = 0.9257 = 92.57%
That is approximately 93% of time results of the repeat FIT give negative results for whom who actually dont have sign of colorectal cancer.
Colonoscopy Abnormal No abnormalities Total Abnormal 22 13 35 Repeat FIT No abnormalities 6 162 168 Total 28 175 203Related Questions
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