Performance characteristics of the suspected blood indicator feature in capsule endoscopy according to indication for study

Background & Aims: The suspected blood indicator (SBI) feature of wireless capsule endoscopy (WCE) was developed for rapid screening of intestinal lesions with bleeding potential. Our aim was to assess the accuracy and performance characteristics of the SBI according to the indications for study in a large cohort of patients. Methods: We reviewed collected data on all WCE studies performed at Johns Hopkins Hospital from January 2006 to June 2007. Study indications were as follows: anemia of unknown origin (n = 53), obscure gastrointestinal bleeding (n = 112), suspected Crohn's disease (n = 122), and other (n = 4). Concordant and discordant findings between gastroenterologists' readings and SBI were recorded for each patient. Results: A total of 221 lesions with bleeding potential was detected. The overall sensitivity, specificity, positive predictive value, and negative predictive value for the SBI were 56.4%, 33.5%, 24.0%, and 67.3%, respectively. For actively bleeding lesions, the SBI sensitivity and positive predictive value were only 58.3% and 70%, respectively. The sensitivity was highest (64%) in patients undergoing WCE for suspected Crohn's disease, with a negative predictive value of 80.4%. The sensitivity was only 58.3% and 41.3%, respectively, in studies performed for obscure gastrointestinal bleeding and anemia. Conclusions: Performance characteristics of the currently available SBI feature in WCE are suboptimal and insufficient to screen for lesions with bleeding potential. Even in patients with active intestinal bleeding, the sensitivity of SBI was less than 60%, which is lower than previously reported. However, in patients with suspected Crohn's disease, the high sensitivity and negative predictive value of SBI may make it a useful tool for the detection of large areas of abnormal mucosa.