Rationale and Objectives
To compare prospectively 64-detector-row computed tomographic colonography (CTC) after a full-laxative tagging-based preparation (full preparation) with a minimum-laxative tagging-based preparation (minimum preparation) with respect to diagnostic performance in the detection of polyps, tagging quality, and patient acceptance.
Materials and Methods
Consecutive 101 patients at high risk for developing colorectal cancer were alternately assigned to either a full preparation group (n = 51) or a minimum preparation group (n = 50) for fecal-tagging CTC. The full preparation consisted of administration of 2-L polyethylene glycol solution with 20 mL of sodium diatrizoate for fecal tagging. The minimum preparation consisted of ingestion of a total of 45 mL of sodium diatrizoate during the 3 days before and 10 mL of sodium picosulfate solution the night before CT. Colonoscopy was used as the reference standard. We assessed the accuracy of polyp detection and the tagging quality for each preparation. All patients were given questionnaires related to their acceptance.
Results
Per-patient sensitivity, specificity, and positive and negative predictive values for polyps ≥ 6 mm were as follows: full preparation group, 97%, 92%, 88%, and 98%, respectively; minimum preparation group, 88%, 68%, 56%, and 92%, respectively. Average visual subjective tagging scores for the full and minimum preparation groups were 94.6% and 76.1%, respectively ( P < .0001). Minimum preparation was better tolerated than full preparation.
Conclusion
Although full-laxative and minimum-laxative fecal-tagging CTC yielded an equally high sensitivity in the detection of polyps ≥ 6 mm, the full-laxative fecal-tagging CTC yielded a better specificity than did the minimum-laxative fecal-tagging CTC. Thus, it is desirable to offer patients an option of either full-laxative fecal-tagging CTC for highest diagnostic accuracy and ability to perform a same-day therapeutic colonoscopy without additional bowel preparation, or minimum-laxative fecal-tagging CTC for those unwilling to undergo full preparation but willing to accept moderate decrease in specificity.
Currently, two types of bowel preparation with fecal tagging are used for computed tomographic colonography (CTC) . The first type is designed to reduce the cleansing procedure as much as possible with fecal tagging for improving patient compliance and acceptance of the preparation . The second type is a conventional, full-laxative preparation with fecal tagging for achieving the cleanest possible colon to yield the best results for polyp detection regardless of patients’ diet or bowel habits . Although clinical trials have been conducted with each bowel preparation regimen, a single trial comparing these two bowel preparation regimens with fecal tagging on a consecutive cohort of patients has not been reported.
Our purpose in this study was prospectively to compare conventional full-laxative with minimum-laxative fecal-tagging CTC in terms of diagnostic performance in the detection of polyps, tagging quality, and patient acceptance in a consecutive patient cohort using 64-detector-row CT scanning.
Materials and methods
Patients and Study Design
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Bowel Preparation for CTC
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Table 1
Patient Characteristics
Characteristics Full Preparation (n = 51) Minimum Preparation (n = 50)P Value Mean age, years ± SD 54.8 ± 15.1 55.4 ± 12.8 0.90 Gender, W/M 16/35 24/26 0.13 Clinical indication to be eligible for examination of total colon (%) 0.44 Hematochezia 19 (37%) 14 (28%) Fecal occult blood 32 (63%) 36 (72%)
Data are numbers of patients, unless otherwise indicated.
Full preparation, full-laxative tagging-based preparation group; minimum preparation, minimum-laxative tagging-based preparation group; SD, standard deviation.
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CT Colonography
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Colonoscopy
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Reference Standard
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Patient Questionnaire
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Table 2
Questionnaire Pertaining to Patient Tolerance and Preference
(For full-laxative tagging-based preparation group) How did you tolerate the full-laxative tagging-based preparation before CT colonography and optical colonoscopy? 1; Well, 2; Fairly well, 3; Indifferent, 4; Fairly poor, 5; Poor (For minimum-laxative tagging-based preparation group) How did you tolerate the minimum-laxative tagging-based preparation before CT colonography? 1; Well, 2; Fairly well, 3; Indifferent, 4; Fairly poor, 5; Poor How did you find the minimum-laxative tagging-based preparation before CT colonography compared with the PEG-based standard pre-colonoscopy preparation? 1; Much better, 2; Better, 3; No difference, 4; Worse, 5; Much worse (For both groups) Since you had both CT colonography and colonoscopy: which examination would you repeat in the future? 1; CT colonography, 2; Colonoscopy, 3; No preference
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Statistical Analysis
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Results
Colonoscopic and Histopathologic Findings
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Table 3
Size and Histopathology Distribution of Polyps by Bowel Preparation Type
Full Preparation Minimum Preparation Number of all polyps 78 34 Number of polyps ≥ 6 mm 32 23 Size (mean ± SD) 8.30 ± 13.6 mm 10.8 ± 12.4 mm Size (distribution) <6 mm 46 (59%) 11 (32%) 6–9 mm 17 (22%) 14 (41%) ≥10 mm 15 (19%) 9 (27%) Histopathology of polyps ≥ 6 mm (distribution) Hyperplastic lesion 4 (13%) 5 (22%) Adenoma 21 (66%) 14 (61%) Cancer 7 (22%) 4 (17%)
Data are polyp numbers, unless otherwise indicated.
Full preparation, full-laxative tagging-based preparation group; minimum preparation, minimum-laxative tagging-based preparation group; SD, standard deviation.
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Tagging Quality
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Diagnostic Performance in the Detection of Polyps on CTC
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Table 4
Per-Patient Diagnostic Performance in the Detection of Polyps ≥ 6 mm
Sensitivity Specificity PPV NPV Overall 93% (98–77) 80% (88–67) 71% (82–54) 95% (99–85) Full preparation 97% (100–74) 92% (98–75) 88% (97–64) 98% (100–83) Minimum preparation 88% (98–62) 68% (83–50) 56% (76–35) 92% (99–74)P value 0.11 0.0005 0.0008 0.11
Data are averages of the performance of the two readers. Numbers in parentheses are 95% confidence intervals.
Full preparation, full-laxative tagging-based preparation group; minimum preparation, minimum-laxative tagging-based preparation group; PPV, positive predictive value; NPV, negative predictive value.
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Table 5
Per-Polyp Diagnostic Performance in the Detection of Polyps ≥ 6 mm
TP FN FP Sensitivity_P_ Value PPV_P_ Value Overall 6–9 mm 25.5 5.5 17 82 (93–63)% 60 (74–43)% ≥10 mm 24 0 3 100 (100–88)% 89 (98–71)% 6–9 mm .49 .013 Full preparation 14.5 2.5 5 85 (96–57)% 74 (91–49)% Minimum preparation 11 3 12 79 (95–49)% 48 (67–29)% ≥10 mm 1.0 .0037 Full preparation 15 0 0 100 (100–82)% 100 (100–82)% Minimum preparation 9 0 3 100 (100–72)% 75 (95–43)% ≥6 mm .37 .0002 Full preparation 29.5 2.5 5 92 (98–75)% 86 (95–69)% Minimum preparation 20 3 15 87 (97–66)% 57 (74–41)%
Data are averages of the numbers of lesions resulting from the two readers, unless otherwise indicated. Numbers in parentheses are 95% confidence intervals.
Full preparation, full-laxative tagging-based preparation group; minimum preparation, minimum-laxative tagging-based preparation group; TP, true-positive; FN, false-negative; FP, false-positive; PPV, positive predictive value.
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Table 6
Causes for False-Positive Findings in Per-Polyp Diagnostic Performance
Total Number Partially Tagged Stool Untagged Stool Fold Thickening Full preparation Reader 1 6 1 0 5 Reader 2 4 0 0 4 Minimum preparation Reader 1 17 7 4 6 Reader 2 13 7 2 4
Data are numbers of false-positive findings.
Full preparation, full-laxative tagging-based preparation group; minimum preparation, minimum-laxative tagging-based preparation group.
Table 7
Causes for False-Negative Findings in Per-Polyp Diagnostic Performance
Total Number Perceptual Error Submerged Polyp in Inhomogeneously Tagged Stool No clear Cause ∗ Full preparation Reader 1 2 2 0 0 Reader 2 3 3 0 0 Minimum preparation Reader 1 2 0 1 1 Reader 2 4 2 1 1
Data are numbers of false-negative findings.
Full preparation, full-laxative tagging-based preparation group; minimum preparation, minimum-laxative tagging-based preparation group.
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Table 8
Agreement between Readers Regarding the Identification of Patients with Colorectal Polyps (Per-Patient for Polyps ≥ 6 mm) and the Presence or Absence of Individual Colorectal Polyps (Per-Polyp ≥ 6 mm)
Per-Patient Per-Polyp Overall 0.90 (0.072) 0.55 (0.075) Full preparation 0.93 (0.12) 0.43 (0.11) Minimum preparation 0.88 (0.094) 0.57 (0.10)
Data are κ coefficients (± standard error). Agreement is considered fair to good if κ values are 0.4–0.75 and excellent if greater than 0.75 . A κ value of zero indicates absence of agreement; negative κ values indicate disagreement .
Full preparation, full-laxative tagging-based preparation group; minimum preparation, minimum-laxative tagging-based preparation group.
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Patient Tolerance and Preference
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Discussion
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Conclusion
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Acknowledgment
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