Background/Aims: Patients of ulcerative colitis (UC) on follow-up are routinely evaluated by sigmoidoscopy. There is no prospective literature to support this practice. We assessed agreement between sigmoidoscopy and colonoscopy prospectively in patients with disease extent beyond the sigmoid colon. Methods: We conducted a prospective observational study at a tertiary care institute for agreement between sigmoidoscopy and colonoscopy. We assessed endoscopic activity using the Mayo Endoscopic Score (MES) and Ulcerative Colitis Endoscopic Index of Severity (UCEIS) and histological activity using the Nancy Index (NI), Robarts Histopathology Index (RHI), and Simplified Geboes Score (SGS). Results: Sigmoidoscopy showed a strong agreement with colonoscopy for MES and UCEIS with a kappa (κ) of 0.96 and 0.94 respectively. The misclassification rate for MES and UCEIS was 3% and 5% respectively. Sigmoidoscopy showed perfect agreement (κ = 1.00) with colonoscopy for assessment of the presence of endoscopic activity in the colon using MES ≥ 1 as activity criteria and strong agreement (κ = 0.93) using MES > 1 as activity criteria. Sigmoidoscopy showed strong agreement with colonoscopy for assessment of the presence of endoscopic activity using UCEIS (κ = 0.92). Strong agreement was observed between sigmoidoscopy and colonoscopy using NI (κ = 0.86), RHI (κ = 1.00), and SGS (κ = 0.92) for the detection of histological activity. The misclassification rate for the detection of histological activity was 2%, 0%, and 1% for NI, RHI, and SGS respectively. Conclusions Sigmoidoscopy showed strong agreement with colonoscopy for endoscopic and histologic disease activity. Sigmoidoscopy is adequate for assessment of disease activity in patients with UC during follow-up evaluation.

Click chemistry has been proven to be very useful in drug delivery. Due to the availability of a large number of click reactions with a various characteristics, selection of appropriate chemistry for a given application is often not a trivial task. This review is written for pharmaceutical researchers who are interested in click chemistry applications and yet may not be click chemistry experts. For this, the review gives an overview of available click reactions organized by application types. Further, the general understanding of click reactions being fast and high yielding sometimes overshadows the need to analyze reaction kinetics in assessing suitability of a given reaction for certain applications. For this, we highlight the need to analyze the relationship among reaction kinetics, concentration effects, and reaction time scales, knowing that lack of such analysis could easily lead to failures. Further, possible issues such as chemical stability with various click reagents are also discussed to aid experimental designs. Recent examples and extensive references are also provided to aid in-depth understanding of technical details. We hope this review will help those interested in using click chemistry in drug delivery to select the appropriate reactions/reagents and minimize the number of pitfalls.