Accuracy of Blood Tracer Technology in Small Bowel Capsule Endoscopy
Vikrant Parihar, Roisin Stack, A. Alakari, Deirdre McNamara*
Departments of Gastroenterology Tallaght Hospital &Trinity College*
Bleeding from the small intestine poses a difficult problem due to its length and looping which makes direct visualization technically challenging and time consuming. Small bowel capsule endoscopy (SBCE) is often used to localize bleeding sources. Capsules are fitted with blood tracer technology which is designed to highlight areas of bleeding within the video and assist rapid reading and analysis.
To determine the accuracy of the blood tracer in clinical practice.
Patients who underwent SBCE were identified retrospectively by using search function and key word bleeding from our database. Patient demographics, indication were recorded. The reports were checked for bleeding. Another reader blinded to the report checked the tracer for red markers suggestive of bleeding. The accuracy of the tracer was compared to the actual report.
To date 100 SBCE’s have been reviewed. The average age of the cohort was 63 years and included 54 males. The three most common indication for SBCE were obscure overt (n= 49) and occult (n= 31) gastrointestinal bleeding and iron deficiency anaemia (n= 13). In 10 patients the SBCE did not reach the caecum, there were no retained capsules. In all Clinicians reported bleeding in 20 cases compared to 56 by the tracer. Overall there were 2 false negative and 36 false positive tracer documented bleeding episodes. The sensitivity, specificity, positive predictive and negative predictive value of the Tracer were 92%, 52%, 32% and 95%. As such if the tracer showed a red mark it was indicative of blood only in one third of cases. However it was highly accurate at predicting bleeding events.
Tracer technology is a simple and reliable quick screening test to rule out active bleeding.