ABSTRACT -- Proposed research objective and approaches: This proposal is aligned with the objective "Evaluation of strategies to translate, disseminate, implement and adopt science-based recommendations and guidelines for the care of acutely injured persons" and with approaches a, c, and e as outlined in this RFA-the evaluation of protocols and guidelines applicable in acute injury care, the determination of the efficacy and impact of various strategies, and the development of methods to validate trauma protocols and guidelines.  Importance: Although chest x-rays (CXRs) reveal diagnostically important information in very few patients, they are the most frequently performed x-rays in blunt trauma patients.  Indiscriminate chest imaging for blunt trauma may generate annual radiographic charges exceeding $900 million, interrupt trauma resuscitations, contribute to emergency department (ED) over-crowding, and expose patients to harmful radiation.1 Objectives: The long-term goal of this project is to reduce unnecessary chest radiography in blunt trauma patients by verifying the following hypotheses: 1) Clinical criteria can reliably identify all blunt trauma patients who have a significant intrathoracic injury (SITI);2) Absence of validated clinical criteria identifies blunt trauma patients who have very low risk of SITI;and 3) Implementing these criteria as a decision instrument could reduce unnecessary CXRs in blunt trauma patients, saving substantial resources without missing SITI.  Study Design, Setting, Participants and Outcome Measures: In this multicenter, prospective study of blunt trauma patients at ten EDs, we will validate a decision instrument that uses clinical criteria to identify patients who have very low risk of SITI visible on plain CXRs.  Decision instrument development requires derivation and validation phases.  With over 3,000 subjects enrolled at three sites over 15 months, we have nearly completed the derivation, in which clinicians document clinical criteria in blunt trauma patients and x-ray reports are used to determine whether patients have SITI.  Analysis of the first 1,850 subjects revealed that a combination of four criteria predicts SITI with 100% sensitivity and excludes injury with 100% negative predictive value.  Validation of a guideline based on this instrument would eliminate the need for CXRs in 38% of blunt trauma victims in this manner: Blunt trauma victims who are alert, not intoxicated, not hypoxic, and have no tenderness to chest wall palpation have very low risk of SITI;therefore, clinicians may safely forego CXRs in them.  We are seeking grant support to conduct the validation phase, in which we will apply and analyze the instrument currently being derived in a separate cohort.  This validation cohort will need to be larger (9,524 patients) in order to define adequately narrow confidence limits for its test characteristics and involve a broad sample of EDs with substantial site monitoring.  This will assure its wide applicability and data reliability so that clinicians can apply the decision instrument with appropriate assurance about its quality and validity.  PUBLIC HEALTH RELEVANCE: Project Narrative: Importance: Although chest x-rays (CXRs) reveal diagnostically important information in very few patients, they are the most frequently performed x-rays in blunt trauma patients.  Indiscriminate chest imaging for blunt trauma may generate annual radiographic charges exceeding $900 million, interrupt trauma resuscitations, contribute to emergency department (ED) over-crowding, and expose patients to harmful radiation.1