Factors Determining Diagnostic Yield of Wireless Capsule Endoscopy

Abstract

Introduction: Wireless capsule endoscopy (WCE) has emerged as an important diagnostic work up for evaluation of patients with anemia. The predictive factors for a positive yield of WCW in patients with anemia with or without overt gastrointestinal bleeding are unclear. The aim of the study was to determine factors predicting a positive diagnostic yield of WCE. Methods: We conducted a single-center retrospective chart review of 174 adult patients age 18 and above at a community hospital center who underwent WCE study for unexplained anemia from 2009-2014. Clinical data including prospective laboratory data were reviewed. All patients had negative esophagogastroduodenoscopy (EGD) and colonoscopy. Fisher exact test and logistic regression models were used. Results: Total of 174 patients were reviewed, 87 were male and 87 were female. The mean age was 57.5 years. 78 patients had positive WCE results, 96 were negative. Age was a significant risk factor for a positive WCE result. Patients with a positive study were 6.6 years older than patients with a negative result (61.2 vs 54.6, p=0.015). Each decade of life increased the relative risk of a positive result by 8%. Lower hemoglobin (Hgb) level was also a risk factor for a positive WCE result. Patients with a positive study had a 1.0 mg/dL lower Hgb level than patients with a negative study (9.8 vs 8.8, p=0.01). In comparison to patients with Hgb > 10, those with Hgb < 7mg/dL had a 3.6 fold increased risk of positive WCE (p- value=0.0005), and those with Hgb between 7-10mg/dL had a 1.7 fold increase in the likelihood of a positive WCE (p=0.09) (Fig 2). There was a weak association with coronary artery disease (CAD) or diabetes mellitus (DM) with a having an abnormal finding on a WCE study (OR=2.1, 1.6, p=0.04, 0.09 respectively). There was no association between gender, race, MCV, MCH, and RDW with positive study results. A multivariate analysis revealed age to be the lone significant independent predictor.Figure 2Conclusion: Anemia is a predictor for having a positive WCE study. Diagnostic yield of WCE is higher when the study is conducted for anemic patients. A hemoglobin below 10 mg/dl is a cutoff for positive results and Hgb < 7 mg/dl has a 3.6 fold increased risk of a positive test result. Age is an independent strong risk factor for having a positive WCE result. CAD and DM were also associated with increased risk, but this may be confounded by higher age in this patient group. There was no evidence for association with gender, race, MCV, MCH and RDW.Figure 1