The Prognostic Usefulness of The Lactate/Albumin Ratio For Predicting Clinical Outcomes In Out-Of-Hospital Cardiac Arrest: A Prospective, Multicentre Observational Study (KoCARC Study) Background and Purpose: We aimed to evaluate the lactate/albumin ratio (LAR) to identify its significance as a prognostic marker for favourable neurologic outcome and survival in patients with return of spontaneous circulation after out-of-hospital cardiac arrest (OHCA). Based on the LAR and multiple parameters, we developed new nomograms and externally validated the tools. Methods: We conducted an observational study using a prospective, multicentre registry of out-of-cardiac arrest resuscitation provided by the Korean Cardiac Arrest Research Consortium registry from October 2015 to June 2017. Results: A total of 524 patients were included in this study. An increased LAR was significantly associated with decreased favourable neurologic outcomes (odds ratio [OR] 0.787; 95% confidence interval [CI] 0.630–0.983; P = 0.035) and survival at discharge (OR 0.744; 95% CI 0.638–0.867; P < 0.001). The areas under the curve (AUCs) for predicting neurologic outcome and survival to discharge using the LAR were 0.824 (P < 0.001) and 0.781 (P < 0.001), respectively. A LAR value of more than the optimal cut-off values of 2.82 and 3.62 could significantly improve prediction of decreased favourable neurologic outcome and survival to discharge, respectively. We constructed nomograms based on the multivariate logistic model. The model for predicting favourable neurologic outcomes and survival discharge had AUCs of 0.927 (P < 0.001) and 0.872 (P < 0.001), respectively. Conclusion: The prognostic performance of the LAR was superior to a single measurement of lactate for predicting favourable neurologic outcomes and survival to discharge after OHCA. The newly developed nomograms can provide rapid prediction of probability of clinical outcomes. Address reprint requests to Je Sung You, MD, PhD, Department of Emergency Medicine, Yonsei University College of Medicine, 211 Eonju-Ro, Gangnam-Gu, Seoul 06273, Republic of Korea. E-mail: youjsmd@yuhs.ac Received 13 May, 2019 Revised 28 June, 2019 Accepted 28 June, 2019 Declaration of interest: The authors declare no conflicts of interest. Source of funding: J.S.Y. was supported by the Basic Science Research Program of the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT (NRF-2018R1C1B6006159). S.P.C. and T.K. were supported by a Basic Science Research Program through the National Research Foundation of Korea funded by the Ministry of Science, ICT, and Future Planning (NRF-2017R1A2B4012378). The funding bodies had no role in the design, collection, analysis, or interpretation of this study. J.S.Y. is an investigator on unrelated studies sponsored by Siemens Health Care, which provide research funding to the Yonsei University College of Medicine, Gangnam Severance Hospital. None of the other authors have potential financial conflicts of interest to disclose. Author Contributions: TK, SPC, and JSY conceived and planned the study. They were mainly responsible for the design of the study. TK, YSP, SDS, KCC, SOH, and SPC collected the data. TK, SK, HSL, and JSY were mainly responsible for analysing the data. TK and JSY wrote the first draft of the manuscript. All authors contributed to the interpretation of finding and reviewed the manuscript. All authors reviewed the statistical analyses and made changes to the content of the manuscript. All authors have also provided intellectual contribution to the manuscript. Supplemental digital content is available for this article. Direct URL citation appears in the printed text and is provided in the HTML and PDF versions of this article on the journal's Web site (www.shockjournal.com). © 2019 by the Shock Society