Background:Low-value use of screening colonoscopy is wasteful and potentially harmful to patients. Decreasing low-value colonoscopy prevents procedural complications, saves patient time and reduces patient discomfort, and can improve access by reducing procedural demand. The objective of this study was to develop and validate an electronic measure of screening colonoscopy overuse using ICD-10 codes and then apply this measure to estimate facility-level overuse to target quality improvement initiatives to reduce overuse in a large integrated healthcare system.Methods:Retrospective national observational study of US Veterans undergoing screening colonoscopy at 119 Veterans Health Administration (VHA) endoscopy facilities in 2017. A measure of screening colonoscopy overuse was specified by an expert workgroup, and electronic approximation of the measure numerator and denominator was performed (“electronic measure”). The electronic measure was then validated via manual record review (n=511). Reliability statistics (n=100) were calculated along with diagnostic test characteristics of the electronic measure. The measure was then applied to estimate overall rates of overuse and facility-level variation in overuse among all eligible patients.Results:The electronic measure had high specificity (99%) and moderate sensitivity (46%). Adjusted PPV and NPV were 33% and 95%, respectively. Inter-rater reliability testing revealed near perfect agreement between raters (k=0.81). 269,572 colonoscopies were performed in VHA in 2017 (88,143 classified as screening procedures). Applying the measure to these 88,143 screening colonoscopies, 24.5% were identified as potential overuse. Median facility-level overuse was 22.5%, with substantial variability across facilities (IQR 19.1%–27.0%).Conclusions:An ICD-10-based electronic measure of screening colonoscopy overuse has high specificity and improved sensitivity compared to a previous ICD-9-based measure. Despite increased focus on reducing low-value care and improving access, a quarter of VHA screening colonoscopies in 2017 were identified as potential low-value procedures, with substantial facility-level variability.