The sensitivity and specificity of guaiac and immunochemical fecal occult blood tests for the detection of advanced colonic adenomas and cancer.
OBJECTIVE
Fecal immunochemical tests (FITs) have been developed to address analytical problems inherent in the older guaiac-based fecal occult blood tests (g-FOBTs). Our aim was to compare the performance characteristics of one g-FOBT (Hemoccult II) and two FITs (the Hemoccult ICT and MagStream HemSp) relative to colonoscopy for the detection of colorectal cancer and significant precursor lesions. We also examined whether a 1-day collection strategy would negatively impact test diagnostic performance.


METHODS
We used a prospective observational cohort design in a Canadian population eligible for screening. All participants received colonoscopy after performing the occult blood tests.


RESULTS
One thousand seventy-five individuals were enrolled (mean age 56.3 years, 53.8 % females). Using colonoscopy as the gold standard, the sensitivity for screen-relevant neoplasm was determined for Hemoccult II (7.2, 95 % CI: 1.1-13.4), Hemoccult ICT (23.2 %: 13.2-33.1), and MagStream HemSp using 67 μg/gram stool as the cut-off (23.2 %: 13.2-33.1). The Magstream HemSp, using a cut-off threshold of 30 μg/gram stool, had the lowest specificity at 87.6 % (85.4-89.6), while the Hemoccult II had the highest at 98.8 % (98.1-99.5). Single-day stool testing reduced the false-positive rates of all tests without significantly reducing the sensitivity.


CONCLUSIONS
We found that FITs have a significantly increased sensitivity but reduced specificity for screen-relevant neoplasm compared to g-FOBT using colonoscopy as the gold standard. Optimal threshold levels for hemoglobin detection depend on the desired trade off between sensitivity and false-positive rate. Single-day testing with an FIT may be an option to enhance population compliance with screening.
Division of Gastroenterology, Royal Alexandra Hospital, 10240 Kingsway Ave, Edmonton, AB, T5H 3V9, Canada.
Clarence K W
CK
Wong
Richard N
RN
Fedorak
Connie I
CI
Prosser
Marianne E
ME
Stewart
Sander Veldhuyzen
SV
van Zanten
Daniel C
DC
Sadowski
D000236:Adenoma / Q000175:diagnosis* / Q000473:pathology*; D003110:Colonic Neoplasms / Q000175:diagnosis* / Q000473:pathology*; D003710:Demography; D055088:Early Detection of Cancer / Q000379:methods*; D005189:False Positive Reactions; D005260:Female; D006138:Guaiac; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D009780:Occult Blood; D012680:Sensitivity and Specificity
D006138:Guaiac