Background: Electronic health records (EHRs) can improve communication processes but unique vulnerabilities remain. Failure to follow-up abnormal test results (“missed results”) is a key preventable factor in diagnostic delays in the VHA and often involves EHR-based communication breakdowns. Our work, as well as data from root cause analyses and malpractice claims in the VA, highlights many technical and “social” (i.e., workflow, organizational, people, and policy) variables that affect test results communication and follow-up. Objectives: We will develop and evaluate a new program for surveillance and improvement of test results- related diagnostic safety. This will include development, implementation, and evaluation of a change package (i.e., a catalogue of strategies, change concepts, and action steps that guide participants in their improvement efforts15) that identifies and addresses risks that predispose health systems to missed test results. Unique features & Innovation: In a 2017 National Quality Forum report “Improving Diagnostic Quality and Safety”, several measurement concepts related to test results follow-up were proposed for further development. We developed and tested a novel electronic indicator system of triggers for missed test results, which uses automated methods to find patients meeting specific criteria using Corporate Data Warehouse (CDW) data. Triggers are signals that can identify patients at higher risk of harm and alert providers to review records for potential patient safety events. Our team has used triggers to identify specific data patterns to facilitate selective chart reviews. We have achieved reasonable positive predictive values (PPVs) and negative predictive values (NPVs), and aim to have these tools used at the system level to measure care delays more efficiently. This measurement system has the potential to become a near real-time surveillance system to identify patients whose test results might have been missed. However, identifying safety deficits using triggers within the CDW is only the first step. For these reports to result in improvements, a team (clinical or organization-based) must analyze the data and create a feedback system to generate learning and improvements. Our change package aims to help VA facility-based teams implement a surveillance and improvement program, ensure that safety measurement will translate into action and help them create back-up systems to monitor diagnostic delays. Methods: Working with 2 operational partners (NCPS and VA Primary Care), our specific aims are: Aim 1: Develop and pilot test a “change package” (SAFER Change Package) to provide VA facilities guidance on how to implement a surveillance and feedback program related to missed test results. Aim 2: Evaluate if the “SAFER TRACKS” Intervention (SAFER Change Package delivered using a Virtual Breakthrough Series [VBTS] Collaborative supplemented with automated surveillance data on test results) can reduce missed results...