Quantitative colonoscopic evaluation of relative efficiencies of an immunochemical faecal occult blood test and a sensitive guaiac test for detecting significant colorectal neoplasms.
BACKGROUND
The guaiac faecal occult blood test (G-FOBT), HemoccultSENSA, is sensitive for significant neoplasms [colorectal cancer (CRC), advanced adenomatous polyps (AAP)], but faulted by non-specificity for human haemoglobin (Hb). Quantified, Hb- specific, immunochemical faecal occult blood tests (I-FOBT) are now used.


OBJECTIVE
To (i) compare I-FOBT and G-FOBT efficacy in identifying significant neoplasms and colonoscopy needs for positive tests and (ii) examine number of I-FOBTs needed and test threshold to use for equivalent or better sensitivity than G-FOBT and fewest colonoscopies for positive tests.


METHODS
Three daily G-FOBTs and I-FOBTs were collected and analysed in 330 patients scheduled for colonoscopy.


RESULTS
Colonoscopy found significant neoplasms in 32 patients, 6 CRC, 26 AAP. G-FOBT, sensitivity and specificity were 53.1% (17 neoplasms) and 59.4%, resulting in 8.1 colonoscopies/neoplasm. One I-FOBT having >or=50 ngHb/mL of buffer provided equivalent sensitivity but 94.0% specificity, resulting in 2.1 colonoscopies/neoplasm. By analysing the higher of two I-FOBTs at 50 ngHb/mL threshold, sensitivity increased to 68.8% (22 neoplasms, P = 0.063), specificity fell to 91.9% (P < 0.001), but still required 2.1 colonoscopies/neoplasm.


CONCLUSIONS
In this population, quantified I-FOBT had significantly better specificity than G-FOBT for significant neoplasms, reducing the number of colonoscopies needed/neoplasm detected. Results depend on the number of I-FOBTs performed and the chosen development threshold.
Rozen
P
P
Gastroenterology Department, Rabin Medical Center, Beilinson Hospital, Petach Tikva, Israel. prozen@012.net.il
Levi
Z
Z
Hazazi
R
R
Waked
A
A
Vilkin
A
A
Maoz
E
E
Birkenfeld
S
S
Niv
Y
Y
D000368:Aged; D003111:Colonic Polyps / Q000737:chemistry / Q000175:diagnosis*; D003113:Colonoscopy / Q000379:methods*; D015179:Colorectal Neoplasms / Q000737:chemistry / Q000175:diagnosis*; D005069:Evaluation Studies as Topic; D005260:Female; D006138:Guaiac; D006801:Humans; D007150:Immunohistochemistry; D007202:Indicators and Reagents; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D009780:Occult Blood; D012680:Sensitivity and Specificity
D007202:Indicators and Reagents; D006138:Guaiac