Background and Aim: Because commercial fecal tagging agents are not available in Thailand, we have prepared our own fecal tagging agent and used it for several years. The purpose of the study is to evaluate the diagnostic performance of computed tomographic colonography (CTC) using a hospital made, 30% w/v barium- based fecal tagging agent.
Materials and Methods: Our institutional review board approved this retrospective study and in- formed consent was waived. We assessed 70 Thai adults with colorectal polyps ≥ 6 mm detected at CTC that underwent optical colonoscopy (OC) within 6 months in Ramathibodi Hospital. Two radiologists interpreted CTCs separately and independently and were blinded to the OC results. The sensitivity of CTC was calculated on a per- polyp basis by using an OC as the reference standard. A per- patient positive predictive value using 6 mm as a threshold was also calculated. Interobserver variability for polyp detection at CTC was evaluated by calculating the Kappa inter-rater reliability.
Results: Using 6 mm as a cut-off point, overall sensitivity of CTC was 87.4%. Stratifying polyps into 6- 9 mm, and ≥ 10 mm, sensitivity of CTC was 80.9%, and 93.8%, respectively. Per-patient positive predictive value was 95.7% using a 6 mm as a threshold. The K-value between 2 observers showed high to excellent agreement in identification of polyps both 6-9 mm (97.1%) and ≥10 mm (97.1%).
Conclusion: CTC using a hospital made, 30% w/v barium-based fecal tagging agent is an effective screening modality, and it could replace the commercial fecal tagging agent in our population.
Key words : Computed tomographic colonography, fecal tagging, colorectal polyps