Small-bowel imaging in Crohn's disease: a prospective, blinded, 4 ...

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Small-bowel imaging in Crohn’s diseaseSolem et alprocedure and the willingness to repeat the procedure inthe future.Consensus reference standardAfter the results of the 4 studies (CTE, ileocolonoscopy,CE, and SBFT) were recorded for each patient, the findingsof all of the studies were reviewed at the conclusionof the study period by a consensus panel of co-investigatorsrepresenting each diagnostic modality and a referringgastroenterologist, to establish a consensus global assessmentof SB Crohn’s disease. If there were discordantresults among studies, this discussion necessitated achange of opinion by one or more investigators about theinitial interpretation of the findings of one or more studies.More specifically, the investigator representing one of thediagnostic modalities had to concede that a mistake hadbeen made in the initial interpretation of the SB findingswith their modality. Thus, the reference standard for assessmentof Crohn’s disease activity was the final determinationof the consensus panel (ie, active, suspicious foractive, inactive, or absent). The consensus criterion standardhas previously been used in a prospective trial oftests evaluating perianal Crohn’s disease. 42 After the modifiedreadings were used to establish the consensus referencestandard for SB disease, the original interpretationof each study as recorded on the study forms, was usedto estimate the performance characteristics of the tests.In a prespecified primary analysis, the diagnoses of activeand suspicious SB Crohn’s disease were grouped together,and the diagnoses of inactive or absent diseasewere grouped together, for all reported analyses to detectactive SB Crohn’s. A prespecified secondary analysis wasalso performed for detecting the presence of SB Crohn’sdisease by combining the categories of active, suspicious,and inactive disease, and comparing this group to the absentcategory. (However, the latter results were consistentwith those of active SB Crohn’s, and are therefore not reportedin the Results.)Statistical analysisFor the primary analysis, the sensitivity of each test wascalculated by dividing the number of patients with positivetest results by the number of patients with active or suspiciousSB Crohn’s disease based on the consensus criterionstandard. The specificity of each test was calculated by dividingthe number of patients with negative tests resultsby the number of patients with inactive or absent SBCrohn’s disease based on the consensus criterion standard.The diagnostic accuracy of each test was calculatedby the number of patients with test results in agreementwith the consensus criterion standard divided by the numberof tests performed. Exact binomial 95% confidence intervalswere also reported.The operating characteristics of each SB examinationwere compared to those of CE in the subset of patientshaving both CE and another SB examination. The sensitivity,specificity, and accuracy of CTE, ileocolonoscopy, andSBFT were compared to CE by using McNemar’s test ofpaired proportions. The combined sensitivity, specificity,and accuracy of all pairs of tests that could be consideredwere also estimated against the consensus criterion standard.McNemar’s test was used to compare the performancesof pairs of tests (CE plus CTE vs ileocolonoscopyplus SBFT, CE plus ileocolonoscopy vs CTE plus SBFT,and CTE plus ileocolonoscopy vs CE plus SBFT). Comparisonsof pairs containing a common diagnostic test were notperformed. The P values were not adjusted for multiplecomparisons.RESULTSForty-two patients enrolled in the study (Fig. 1). Onepatient withdrew for personal reasons before any diagnosticstudies were performed and was not included in theanalysis. The median age of the 41 patients (81% female)participating in the study was 40.1 years (range 18.9-73.5years). Forty-one patients underwent CTE. One patientsubsequently withdrew for personal reasons and had nofurther studies. Ileoscopy was feasible in 36 of the 40 colonoscopies.Thirty-eight patients had SBFT examinationsafter 1 patient exited the study due to a stricture detectedon CTE, and 1 patient underwent surgery for a PSBO.Twenty-eight patients had CE studies after 10 patientswere excluded for PSBO or abscess, and 2 patients leftthe study for personal reasons. One capsule study was repeateddue to a technical malfunction with the initialexamination (no images were obtained), and one capsulewas retained in the stomach for the duration of batterylife, resulting in no SB images (but the capsule eventuallypassed spontaneously). Twenty-seven capsule studieswere then used for analysis. Table 1 details the combinationsof the 4 SB examinations patients received.The study co-investigators were able to reach a consensusopinion regarding the global assessment of SB Crohn’sdisease after unblinding at the conclusion of study in all 41patients who had one or more SB studies (Table 2). Thefinal clinical diagnoses for all patients, not limited to theSB, are reported in Table 3.Table 4 reports the sensitivity, specificity, and accuracyof the 4 SB tests individually, with the consensus criterionstandard used to classify patient status as either ‘‘active’’(active plus suspicious) or ‘‘inactive’’ (inactive plus absent).The sensitivity for the detection of active SB Crohn’sdisease was 83% for CE, 82% for CTE, 74% for ileocolonoscopy,and 65% for SBFT. The specificity for SB Crohn’sdisease was 100% for ileocolonoscopy, 94% for SBFT,89% for CTE, and 53% for CE. The overall accuracy forSB Crohn’s was 86% for ileocolonoscopy, 85% for CTE,79% for SBFT, and 67% for CE.The performance of CTE, ileocolonoscopy, and SBFTwere each compared with that of CE (Table 5). There258 GASTROINTESTINAL ENDOSCOPY Volume 68, No. 2 : 2008 www.giejournal.org
Solem et alSmall-bowel imaging in Crohn’s diseaseFigure 1. A graphic representation of patient movement throughout the course of the study.TABLE 1. Combinations of the 4 SB examinationsundergone by 42 participants initially enrolled inthe studyCE(n Z 27)Ileocolonoscopy(n Z 36)SBFT(n Z 38)CTE(n Z 41)No.patientsNo No No No 1No No No Yes 1No No Yes Yes 3No Yes No Yes 2No Yes Yes Yes 8Yes No Yes Yes 1Yes Yes Yes Yes 26CE, Capsule endoscopy; SBFT, small bowel follow-through; CTE,computed tomographic enterography.were 12 patients in each of 3 sensitivity comparisons, andfor specificity there were 15 patients, except to compareCE versus SBFT, where only 14 received both examinations.The sensitivity of CE (83%) was not significantly differentfrom that of CTE (67%, P Z .63), ileocolonoscopy(67%, P Z .69), or SBFT (50%, P Z .22). However, thespecificity of CE (53%) was significantly lower than thatfor either CTE (100%, P Z .02) or SBFT (100%, P Z.02). The specificity of CE (43%) was also significantlylower among the 14 patients having ileocolonoscopy(100%, P Z .03). The lower specificity of CE was due toTABLE 2. Final consensus diagnosis for small-bowelCrohn’s disease in 41 patients who underwent at least 1diagnostic test, and in 26 patients who underwent all 4testsSmall-bowel Crohn’sdisease diagnosisAll patients,n (%)*Patients withall 4 tests, n (%)yActive 21 (51) 11 (42)Absent 17 (42) 12 (46)Inactive 2 (5) 2 (8)Suspicious 1 (2) 1 (4)Total 41 (100) 26 (100)*Percentage of the group undergoing at least 1 SB imaging test.yPercentage of the group undergoing all 4 tests.the fact that, in 7 patients, there were findings that ledthe CE reader to deem the examination either suspicious(n Z 5) or ‘‘definite’’ (n Z 2) for active Crohn’s disease,but according to the consensus criterion standard, thesepatients had either no evidence of Crohn’s disease (n Z5) or only inactive disease (n Z 2).The performance characteristics of pairs of SB examinationsagainst the consensus criterion standard were estimated(Table 4). A patient was classified positive foractive SB Crohn’s disease if either of the 2 examinationsindicated active disease. The sensitivity for combinationsof examinations ranged from a high of 100% for the CEand ileocolonoscopy combination to a low of 78% forwww.giejournal.org Volume 68, No. 2 : 2008 GASTROINTESTINAL ENDOSCOPY 259
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