CT colonography before colonoscopy in subjects with positive faecal occult blood test. Preliminary experience.
OBJECTIVE
We report a preliminary evaluation of the performance of computed tomography colonography (CTC) systematically obtained before optical colonoscopy (OC) in subjects with positive faecal occult blood test (FOBT) within a population-based screening programme for colorectal cancer (CRC).


METHODS
Seventy-nine subjects with positive FOBT from a regional screening programme were invited to perform same day CTC and OC. CTC was performed with standard bowel preparation. OC with segmental unblinding was the reference standard. A per-patient per-adenoma analysis was performed.


RESULTS
Forty-nine of 79 subjects (62%) with positive FOBT adhered to the study and completed both examinations. Twenty-two (44.9%) of the 49 had a cancer or an adenoma ≥6 mm. Per-patient sensitivity, specificity, negative predictive value and positive predictive value for cancer or adenoma ≥6 mm were 95.5% (95%CI:77.2%-99.9%), 51.9% (95%CI:32.0%-71.3%), 93.3% (95%CI:68.1%-99.8%) and 61.8% (95%CI:43.6%-77.8%).


CONCLUSIONS
In the setting of a FOBT-based screening programme for CRC, CTC showed a high sensitivity, but relatively low specificity and positive predictive value, for cancer and adenoma ≥6 mm. Probably performing CTC without faecal tagging as second line test after a positive FOBT is not a cost-effective strategy.
Sali
L
L
Radiodiagnostic Section--Department of Clinical Physiopathology, University of Florence, Viale G.B. Morgagni 85, Florence, Italy. lapo.sali@unifi.it
Falchini
M
M
Della Monica
P
P
Regge
D
D
Bonanomi
A G
AG
Castiglione
G
G
Grazzini
G
G
Zappa
M
M
Mungai
F
F
Volpe
C
C
Mascalchi
M
M
D000368:Aged; D023881:Colonography, Computed Tomographic / Q000379:methods*; D003113:Colonoscopy; D015179:Colorectal Neoplasms / Q000175:diagnosis / Q000000981:diagnostic imaging* / Q000453:epidemiology; D005260:Female; D006801:Humans; D007558:Italy / Q000453:epidemiology; D008297:Male; D008403:Mass Screening; D008875:Middle Aged; D009780:Occult Blood; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011857:Radiographic Image Interpretation, Computer-Assisted; D012680:Sensitivity and Specificity