A208 OPTIMIZING THE UTILITY OF CT ENTEROGRAPHY FOR THE EVALUATION OF OBSCURE GASTROINTESTINAL BLEEDING: A NOVEL HIGHLY SENSITIVE CLINICAL PREDICTION TOOL

Computed tomography (CTE) and capsule endoscopy (CE) are common modalities used to investigate obscure GI bleeds (OGIB). Although recent guidelines recommend CE before CTE as the first modality to evaluate OGIB, CTE offers multiple advantages including lower cost, greater availability, and the ability to detect strictures, masses, and extraluminal pathology. It is not yet clear which OGIB patients would most benefit from CTE before CE. Our study sought to determine patient factors associated with positive CTE in OGIB patients to develop a novel clinical decision tool to predict which patients are more likely versus less likely to have a diagnostic CTE. This was a retrospective study using patients who underwent CTE for OGIB defined as a suspected gastrointestinal (GI) bleed with no cause identified on gastroscope or colonoscopy at The Ottawa Hospital between 2005- 2015. Factors (symptoms, history, investigations, interventions, outcomes) selected a priori from literature review were collected by chart review. Logistic regression with univariate and multivariate analysis were performed to identify factors associated with a positive CTE study. Of 147 patients with OGIB, CTE was positive in 1 in 5 cases (n=31, 21%). 22 (71%) of the CTE positive cases had at least one of intestinal wall thickening, angiodysplasias, suspected bowel mass, or concerning stricture. The presence of overt GI bleeding (OR 12.4, 95% CI 1.6–95.0), abdominal or constitutional symptoms (OR 2.9, 95% CI 1.2–7.0), or a personal history of GI cancer (OR 17.5, 95% CI 1.9–163.5) were factors that predicted a positive CTE study with univariate analysis. This was also seen in multivariate analysis (OR 13.3, 95% CI 1.5–121.9; OR 2.5, 95% CI 1.0–6.6; OR 30.3, 95% CI 1.4–634.2 respectively). Absence of these 3 factors was associated with zero likelihood of having a positive CTE, while presence of any of these factors was associated with a 1 in 4 likelihood of having a positive CTE. A rule based on the absence of these factors for predicting a positive CTE would have a sensitivity, specificity, negative predictive value, and positive predictive value of 100% (95% CI 80–100%), 16% (95% CI 10–24%), 100%, and 24% (95% CI 23–26%) respectively. CTE can be diagnostic in 1 in 5 cases of OGIB. Diagnostic yield may be greater for patients with overt GI bleeding, abdominal and/or constitutional symptoms, or a personal history of GI malignancy. Absence of these 3 factors was associated with zero likelihood of a positive CTE. Together, these factors can function as a highly sensitive tool to predict which OGIB patients are unlikely to have a diagnostic CTE. This can potentially reduce non-diagnostic CTE and avoid the need for CE. Future research to validate this tool in other populations with OGIB are needed. None

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