The effect of diagnostic confidence on the probability of optical colonoscopic confirmation of potential polyps detected on CT colonography: prospective assessment in 1,339 asymptomatic adults.

OBJECTIVE: We sought to evaluate the effect of interpreter confidence on the likelihood that a lesion detected on CT colonography (CTC) will correspond to a matched polyp seen on optical colonoscopy. SUBJECTS AND METHODS: Same-day CTC and optical colonoscopy were performed on 1,339 asymptomatic adults. A standard matching algorithm for polyp size and location was used. For each potential polyp detected on CTC, the level of diagnostic confidence was prospectively rated on a 3-point scale (1, least certain; 2, intermediate; and 3, most certain). RESULTS: For CTC-detected lesions 6 mm or larger, diagnostic confidence levels of 1, 2, and 3 corresponded to matched polyps on optical colonoscopy in 33.3% (45/135), 50.0% (103/206), and 66.8% (157/235) of cases, respectively (p < 0.01). Similar trends were present for categories of lesions that measured 6-7 mm, 8-9 mm, and 10 mm or larger, rising to a match rate of 82.1% (55/67) for lesions 10 mm or larger that were diagnosed with a level-3 confidence rating. The likelihood that a matched polyp was adenomatous increased with greater levels of diagnostic confidence. Of note, level-3 confidence for lesions measuring 8-9 mm on CTC more often yielded a matching neoplasm on optical colonoscopy than level-1 or level-2 confidence for lesions measuring 10 mm or larger (60.3% [35/58] vs 20.8% [10/48]; p < 0.0001). CONCLUSION: Greater diagnostic confidence for an individual lesion detected on CTC correlates with a significantly increased likelihood that a matching polyp will be found on optical colonoscopy and that this matched polyp will be neoplastic. Although polyp size represents the primary criterion for CTC screening algorithms, this data could help guide the decision to opt for noninvasive CTC surveillance versus optical colonoscopy for polypectomy.

Flat colorectal lesions in asymptomatic adults: implications for screening with CT virtual colonoscopy.

OBJECTIVE: The clinical significance of flat lesions in colorectal cancer screening remains uncertain. The purpose of this study was to investigate the frequency, histology, and virtual colonoscopy detection of flat lesions in an asymptomatic screening population. SUBJECTS AND METHODS: The morphology of all detected polyps was prospectively recorded as flat or polypoid (sessile or pedunculated) in 1,233 consecutive asymptomatic adults who underwent same-day virtual colonoscopy and optical colonoscopy. A flat morphology was defined as a shallow plaquelike broad-based lesion with a height of less than one half of its width. RESULTS: Of 344 polyps of 6 mm or greater confirmed at optical colonoscopy, 17 (4.9%) were labeled as flat at both virtual colonoscopy and optical colonoscopy; 17 (4.9%), at optical colonoscopy only; and 25 (7.3%), at virtual colonoscopy only, yielding 59 total lesions in 52 (4.2%) of 1,233 patients. Twenty-nine (49.2%) of 59 flat lesions were adenomatous, of which four measured 10 mm or greater and one 6- to 9-mm lesion was histologically advanced. None of the 148 diminutive flat lesions (< or = 5 mm) detected at optical colonoscopy was histologically advanced. Virtual colonoscopy prospectively detected 24 (82.8%) of 29 flat adenomas and 47 (80.0%) of all 59 flat lesions 6 mm or greater. In comparison, the sensitivity of virtual colonoscopy for the detection of polypoid adenomas and all polypoid lesions of 6 mm or greater was 86.2% (156/181, p = 0.58) and 81.0% (231/285, p = 0.86), respectively. CONCLUSION: Flat adenomas measuring 6 mm or greater are uncommon in a typical Western screening population, and advanced flat neoplasms are rare. The sensitivity of virtual colonoscopy for detecting flat lesions was similar to that of polypoid lesions. These results indicate that flat lesions are not a significant drawback for virtual colonoscopy screening.

Location of adenomas missed by optical colonoscopy.

BACKGROUND: Previous estimates of the adenoma miss rate with optical colonoscopy (OC) are hindered by the use of OC as its own reference standard. OBJECTIVE: To evaluate the frequency and characteristics of colorectal neoplasms that are missed prospectively on OC by using virtual colonoscopy (VC) as a separate reference standard. DESIGN: Prospective, multicenter screening trial. SETTING: 3 medical centers. PARTICIPANTS: 1233 asymptomatic adults who underwent same-day VC and OC. MEASUREMENTS: Colorectal neoplasms (adenomatous polyps) missed at OC before VC results were unblinded. RESULTS: Fourteen (93.3%) of 15 nonrectal neoplasms were located on a fold; 10 (71.4%) of these were located on the backside of a fold. Five (83.3%) of 6 rectal lesions were located within 10 cm of the anal verge. LIMITATIONS: Estimation of the OC miss rate depended on polyp detection on both VC and second-look OC and therefore underestimates the true OC miss rate, particularly for smaller polyps. CONCLUSIONS: Most clinically significant adenomas missed prospectively on OC are located behind a fold or near the anal verge. The 12% OC miss rate for large adenomas (>or=10 mm) when state-of-the-art 3-dimensional VC is used as a separate reference standard is increased from the previous 0% to 6% estimates derived by using OC as its own reference standard.

Computed tomographic virtual colonoscopy to screen for colorectal neoplasia in asymptomatic adults.

BACKGROUND: We evaluated the performance characteristics of computed tomographic (CT) virtual colonoscopy for the detection of colorectal neoplasia in an average-risk screening population. METHODS: A total of 1233 asymptomatic adults (mean age, 57.8 years) underwent same-day virtual and optical colonoscopy. Radiologists used the three-dimensional endoluminal display for the initial detection of polyps on CT virtual colonoscopy. For the initial examination of each colonic segment, the colonoscopists were unaware of the findings on virtual colonoscopy, which were revealed to them before any subsequent reexamination. The sensitivity and specificity of virtual colonoscopy and the sensitivity of optical colonoscopy were calculated with the use of the findings of the final, unblinded optical colonoscopy as the reference standard. RESULTS: The sensitivity of virtual colonoscopy for adenomatous polyps was 93.8 percent for polyps at least 10 mm in diameter, 93.9 percent for polyps at least 8 mm in diameter, and 88.7 percent for polyps at least 6 mm in diameter. The sensitivity of optical colonoscopy for adenomatous polyps was 87.5 percent, 91.5 percent, and 92.3 percent for the three sizes of polyps, respectively. The specificity of virtual colonoscopy for adenomatous polyps was 96.0 percent for polyps at least 10 mm in diameter, 92.2 percent for polyps at least 8 mm in diameter, and 79.6 percent for polyps at least 6 mm in diameter. Two polyps were malignant; both were detected on virtual colonoscopy, and one of them was missed on optical colonoscopy before the results on virtual colonoscopy were revealed. CONCLUSIONS: CT virtual colonoscopy with the use of a three-dimensional approach is an accurate screening method for the detection of colorectal neoplasia in asymptomatic average-risk adults and compares favorably with optical colonoscopy in terms of the detection of clinically relevant lesions.