Diagnostic Value of Rectal Bleeding in Predicting Colorectal Cancer: a Systematic Review

This study aimed at summarizing published study findings on the diagnostic value of rectal bleeding (RB)and informing clinical practice, preventive interventions and future research areas. We searched Medline andEmbase for studies published by September 13, 2013 examining the risk of colorectal cancer in patients with RBusing highly inclusive algorithms. Data for sensitivity, specificity, positive likelihood ratio, negative likelihood ratioand positive predictive value (PPV) of RB were extracted by two researchers and analyzed applying Meta-Disc(version 1.4) and Stata (version 11.0). Methodological quality of studies was assessed according to QUADAS. Atotal of 38 studies containing 5,626 colorectal cancer patients and 73,174 participants with RB were included. Thepooled sensitivity and specificity were 0.47 (95% CI: 0.45-0.48) and 0.96 (95% CI: 0.96-0.96) respectively. Theoverall PPVs ranged from 0.01 to 0.21 with a pooled value of 0.06 (95% CI: 0.05-0.08). Being over the age of 60years, change in bowel habit, weight loss, anaemia, colorectal cancer among first-degree relatives and feeling ofincomplete evacuation of rectum appeared to increase the predictive value of RB. Although RB greatly increasesthe probability of diagnosing colorectal cancer, it alone may not be sufficient for proposing further sophisticatedinvestigations. However, given the high specificity, subjects without RB may be ruled out of further investigations.Future studies should focus on strategies using RB as an “alarm” symptom and finding additional indicationsto justify whether there is a need for further investigations.