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

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Small-bowel imaging in Crohn’s diseaseSolem et alTABLE 3. Final overall clinical diagnosis (not limited tothe small intestine) in all 41 patients who underwent atleast 1 diagnostic test, and in 26 patients whounderwent all 4 testsClinicaldiagnosisAllpatients,n (%)*Patientswith all 4tests, n (%)yCrohn’s disease 30 (73%) 19 (73%)Indeterminate abdominal pain 3 (7%) 3 (11%)Irritable bowel syndrome 2 (5%) 2 (8%)Ulcerative colitis 1 (2%) 0 (0%)Indeterminate colitis 1 (2%) 0 (0%)Carcinoid 1 (2%) 0 (0%)Submucosal mass, small bowel 1 (2%) 1 (4%)Gastroparesis 1 (2%) 1 (4%)Indeterminate diarrhea 1 (2%) 0 (0%)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 ileocolonoscopy and SBFT combination. The specificityof examination combinations against the criterion standardranged from a high of 100% for SBFT plusileocolonoscopy to a low of 53% for both the CE plusSBFT and CE plus CTE combinations. The overall accuracyof examination combinations against the criterion standardranged from 89% for both the CTE plus ileocolonoscopyand CTE plus SBFT combinations to 70% for theCE plus CTE and CE plus SBFT combinations.No pair of SB examinations was significantly more sensitivethan the combination containing the other two examinations(among the 4 SB examinations), P O .05(Table 6). However, each combination of examinationsthat included CE had a significantly lower specificity(57%) than did the opposite pair of examinations (P Z.03 for each of the 3 comparisons, unadjusted).Patients completed a questionnaire at the end of thestudy. All patients swallowed the capsule easily. Ninetytwopercent of patients did not experience any pain duringthe CE study, significantly better than colonoscopy(P ! .05), but no better than CTE or SBFT (P O .05).Ninety-three percent of patients stated they would undergoa CE study again, which was not significantly differentthan the other tests (P O .05).Even though all patients with obstructive symptomswere excluded from study enrollment, we detected anasymptomatic PSBO in 7 patients (17%) on CTE (Fig. 2),excluding them from CE. Soon after capsule ingestion,one patient with a very long segment of active diseasebut without PSBO on CTE (3.4%) experienced a highlysymptomatic PSBO requiring hospitalization, but the capsulepassed within a few days following medical therapywith corticosteroids and infliximab, with symptoms resolving(Fig. 3). Unlike the higher capsule retention rates seenin other studies, we had no retained capsules (confirmedby radiograph) using our diagnostic algorithm.Chyme significantly limited study quality in 4 patientswho underwent CE (14%) despite efforts to cleanse with1 L PEG solution prior to the study. The terminal ileumwas examined completely in only 75% of studies. One capsulestudy had a technical malfunction resulting in no images.In a single patient with suspected Crohn’s disease,CE demonstrated multiple SB erosions when the other 3SB tests were normal (Fig. 4).DISCUSSIONIn this prospective, blinded trial, we compared 4 primarysmall-intestinal imaging modalities in the diagnosisof SB Crohn’s disease. In contrast to the other studies examiningthe utility of CE in patients with known or suspectedCrohn’s disease, 22,27,29,33-40 we believe this is theonly prospective, blinded trial comparing all 4 primarySB imaging modalities over a short time period, avoidingboth treatment and natural history effects. Unlike the ‘‘diagnosticyield’’ reported in most published CE studies, weestablished a surrogate criterion standard, allowing us tocalculate the sensitivity, specificity, and accuracy of eachtest for diagnosing SB Crohn’s disease. We found thatthere was no significant difference among CTE, CE, ileocolonoscopy,and SBFT for the sensitivity or accuracy of diagnosingSB Crohn’s disease. CTE and CE demonstratedsimilarly high sensitivity for SB Crohn’s, which was numericallysuperior to SBFT and ileocolonoscopy. Although thenumerical superiority of CTE and CE was not statisticallysignificant, this may have been due to the limited samplesize and potential lack of power to detect a significant difference.Combining diagnostic tests may improve sensitivity,and this is commonly used in clinical practice. Wefound that the specificity of CE for SB Crohn’s diseasewas significantly lower than other SB imaging modalities,which lowered its overall accuracy. Our study also indirectlysuggests that SB radiologic imaging may be neededprior to CE in suspected or known Crohn’s disease patients,due to the high frequency (17%) of asymptomaticPSBO. When we used an algorithm of performing CTEprior to CE and using a finding of stricture with proximalbowel dilation to preclude ingestion of the endoscopycapsule, we observed no capsule retention.The finding of a lower specificity of CE for SB Crohn’sdisease is not entirely unexpected. ‘‘Diagnostic yield’’ asa measure of the operating performance of a diagnostictest is less than idealdit merely reports the prevalenceof abnormalities detected by a particular imaging modalityand does not attempt to determine whether those260 GASTROINTESTINAL ENDOSCOPY Volume 68, No. 2 : 2008 www.giejournal.org
Solem et alSmall-bowel imaging in Crohn’s diseaseTABLE 4. Individual performance estimates of 4 diagnostic tests and all pairs of these tests for active small-bowel Crohn’s disease*SB test Patients tested, n Sensitivity (%) 95% CI Specificity (%) 95% CI Accuracy (%) 95% CIIndividual testCE 27 10/12 (83) 52-98 8/15 (53) 27-79 18/27 (67) 46-83CTE 41 18/22 (82) 60-95 17/19 (89) 67-99 35/41 (85) 71-94Ileocolonoscopy 36 14/19 (74) 49-91 17/17 (100) 80-100 31/36 (86) 71-95SBFT 38 13/20 (65) 41-8 17/18 (94) 73-100 30/38 (79) 63-90Pairs of TestsCE & CTE 27 11/12 (92) 62-100 8/15 (53) 27-79 19/27 (70) 50-86CE & ileocolonoscopy 26 12/12 (100) 74-100 8/14 (57) 29-82 20/26 (77) 56-91CE & SBFT 27 11/12 (92) 62-100 8/15 (53) 27-79 19/27 (70) 50-86SBFT & ileocolonoscopy 34 14/18 (78) 52-94 16/16 (100) 79-100 30/34 (88) 73-97CTE & ileocolonoscopy 36 16/19 (84) 60-97 16/17 (94) 71-100 32/36 (89) 74-97CTE & SBFT 38 17/20 (85) 62-97 17/18 (94) 73-100 34/38 (89) 75-97CTE, CT enterography; CE, capsule endoscopy; SBFT, small-bowel follow-through; 95% CI, 95% confidence intervals.*Criterion standard is based on consensus diagnosis of active Crohn’s disease or suspicious for Crohn’s disease.TABLE 5. Comparison of sensitivity and specificitybetween capsule endoscopy and 3 other diagnostictests for active small-bowel Crohn’s disease*SB testSensitivity(%)P-valueySpecificity(%)P-valueyCE 10/12 (83) ref 8/15 (53) refCTE 8/12 (67) .63 15/15 (100) .02Ileocolonoscopy 8/12 (67) .69 14/14 (100) .03SBFT 6/12 (50) .22 15/15 (100) .02CTE, CT enterography; CE, capsule endoscopy; SBFT, small-bowelfollow-through; 95% CI, 95% confidence intervals.*Criterion standard is based on consensus diagnosis of activeCrohn’s disease or suspicious for Crohn’s disease.yUsing Mc Nemar’s test for paired proportions, testing performancecompared to the CE examination, unadjusted for multiplecomparisons.abnormal findings are clinically significant. Most studiesreporting ‘‘diagnostic yield’’ do so because the test isnot being compared against a reference standard. CE isan extremely sensitive tool for direct visualization ofthe SB mucosa. As in most diagnostic tests, improvedsensitivity typically comes at the cost of decreased specificity.43 Goldstein et al 44 found that 22% of asymptomaticcontrol patients who denied recent NSAID ingestion hadSB abnormalities at CE, with an average of 4 lesions persubject. As several CE findings, such as mucosal erythema,are nonspecific, and do not indicate a diagnosisof active Crohn’s disease by themselves, their inclusionTABLE 6. Selected comparisons of sensitivity andspecificity between pairs of small-bowel examinations*CE &ileocolonoscopySensitivity(%)P- Specificityvaluey (%)12/12 (100) 8/14 (57)P-valueyCTE & SBFT 9/12 (75) .25 14/14 (100) .03CE & CTE 11/12 (92) 8/14 (57)SBFT &ileocolonoscopy9/12 (75) .63 14/14 (100) .03CE & SBFT 11/12 (92) 8/14 (57)CTE &ileocolonoscopy9/12 (75) .63 14/14 (100) .03CTE, CT enterography; CE, capsule endoscopy; SBFT, small-bowelfollow-through; 95% CI, 95% confidence intervals.*Criterion standard is based on consensus diagnosis of activeCrohn’s disease or suspicious for Crohn’s disease.yUsing McNemar’s test for paired proportions, unadjusted formultiple comparisons.into reference standard assessments of disease activityin SB imaging trials may result in confirmation bias favoringCE.Buchman et al 36 used SBFT as a method to detect SBstrictures that may lead to retained capsules, and founda 29% incidence of SB strictures in Crohn’s patients, whichprecluded capsule endoscopy. By using SBFT as a screeningexamination, they observed 2 episodes of capsule retention(7%). Voderholzer et al 27 compared CE and CTEwww.giejournal.org Volume 68, No. 2 : 2008 GASTROINTESTINAL ENDOSCOPY 261
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