Background:Futile resuscitation for out-of-hospital cardiac arrest (OHCA) patients in the COVID-19 era can lead to risk of disease transmission and unnecessary transport. Various existing basic or advanced life support (BLS or ALS) rules for termination of resuscitation (TOR)have been derived and validated in North America and Asian countries. This study aimed to evaluate the external validation of these rules in predicting the survival outcomes of OHCA patients in the COVID-19 era.Methods: A multicenter observational study was performed using the WinCOVID-19 Daegu registry data collected from 18 February to 31March 2020. The outcomes of each rule were compared to the actual patient survival outcomes. The sensitivity, specificity, false positive ratio (FPR), and positive predictive value (PPV) of each TOR rule were evaluated. Results: Of the 184 OHCA patients, 170 patients,who showed cardiac arrest of presumed cardiac etiology, were enrolled. TOR was recommended for 122 patientsbased on the international BLS-TOR rule, which showed 85% specificity, 74% sensitivity, 0.8% FPR, and 99% PPV for predicting unfavorable survival outcomes. When the traditional BLS-TOR rules and KoCARC TOR rule II were applied to our registry, one patient met the TOR criteria but survived at hospital discharge. With regard to the FPR (upper limit of 95% confidence interval<5%) and PPV (>99%) criteria, only the KoCARCTOR rule I, which included a combination ofthree factors including not being witnessed by emergency medical technicians, presenting with an asystole at the scene, and not experiencing prehospital shock delivery or ROSC, was found to be superiorto all other TOR rules. Conclusion: Among the previous nine BLS and ALS TOR rules, KoCARCTOR rule I was most suitable for predicting poor survival outcomes and showed improved diagnostic performance. Further research on variations in resources and treatment protocols among facilities, regions, and cultures will be useful in determining the feasibility of TOR rules for COVID-19 patients worldwide.Trial registration: Not applicable