Clinical factors related to false-positive rates of patency capsule examination

BACKGROUND Retention is the most common complication of capsule endoscopy (CE), and is reported to occur in 0-13% of cases. To avoid retention, a PillCam patency capsule (PC) is used in patients with suspected intestinal stenosis. However, a relatively low positive predictive value of the PC examination has been reported previously. The aims of this study were to clarify the accuracy of PC examination and to evaluate clinical factors related to cases of false-positive detection. METHODS We performed a retrospective single-center study of 282 consecutive patients referred for PC examination. Patients in which the PC could not pass through the small bowel within 33 h were classified into the 'no patency' group. The 'no patency' group was investigated for evidence of significant stenosis upon further examinations, including CE, double-balloon endoscopy, and small bowel follow-through after PC examination. Clinical factors related to small bowel patency and false-positive cases were evaluated. RESULTS We included 161 male (57.1%) and 121 female (42.9%) patients with a mean age of 47.5 ± 17.7 years. Of the 282 patients enrolled, 27 patients exhibited 'no patency' upon PC examination. Multivariate analysis showed that clinical factors related to 'no patency' included Crohn's disease, abdominal symptoms, stenosis upon imaging, and previous abdominal surgery. Upon further examination, nine cases in the 'no patency' group had significant stenosis. Sensitivity, specificity, and negative and positive predictive values of PC examination for detecting small bowel stenosis were 93.8%, 96.6%, 99.6%, and 62.5%, respectively, and the only clinical factor related to false-positive cases was constipation (p < 0.05). CONCLUSION We found a relatively low positive predictive value of PC examination and that constipation was related to false-positive results. To extend the implications of CE indications, clinical study focusing on these results is expected.