Objective: The study aims to determine the latent class of roles in bullying victimization and perpetration among primary and secondary school students and to explore its relationship with academic achievement and screen use, to provide a reference for developing preventive measures and intervention plans. Methods: A total of 29 099 students at grade 5,6,7,8,10, and 11 from Shenzhen were surveyed through convenient cluster sampling method by Olweus Bully/Victim Questionnaire. The latent class analysis was used for classifying bully/victim category. Results: The latent class analysis revealed three classes, the noninvolvement group (low response rate at all items, 80.9%), the bullying victimization group (low response rate at bullying and high response rate at victimization items, 15.9%), and the bullying victimization and perpetration group (high response rate at all items,3.3%). Boys were more likely than girls to belong to the bullying victimization and perpetration at all study sections ( OR =0.83,0.74, 0.47 , P <0.05). Transfer students were at higher risk to be in the bullying victimization group in elementary and middle school ( OR = 1.21 ,1.21), while they were more likely to fall into the bullying victimization and perpetration group in high school ( OR =2.65)( P < 0.05). Students with poor academic performance were more likely to be in the bullying victimization group at all sections ( OR = 0.98 ,0.98,0.98) and in the bullying victimization and perpetration group at elementary and middle school ( OR =0.97, 0.98)( P < 0.05 ). Students spending longer time on screen had elevated risk in the bullying victimization group ( OR =1.06,1.04,1.08, P < 0.05 ). Conclusion Students with poor academic achievement and prolonged screen time are at higher risks to be involved in bullying victimization and perpetration. Collaboration between home and school are needed to preventing bullying victimization perpetration.

Patients with severe trauma require an extremely timely treatment and transfusion plays an irreplaceable role in the emergency treatment of such patients. An increasing number of evidence-based medicinal evidences and clinical practices suggest that patients with severe traumatic bleeding benefit from early transfusion of low-titer group O whole blood or hemostatic resuscitation with red blood cells, plasma and platelet of a balanced ratio. However, the current domestic mode of blood supply cannot fully meet the requirements of timely and effective blood transfusion for emergency treatment of patients with severe trauma in clinical practice. In order to solve the key problems in blood supply and blood transfusion strategies for emergency treatment of severe trauma, Branch of Clinical Transfusion Medicine of Chinese Medical Association, Group for Trauma Emergency Care and Multiple Injuries of Trauma Branch of Chinese Medical Association, Young Scholar Group of Disaster Medicine Branch of Chinese Medical Association organized domestic experts of blood transfusion medicine and trauma treatment to jointly formulate Chinese expert consensus on blood support mode and blood transfusion strategies for emergency treatment of severe trauma patients ( version 2024). Based on the evidence-based medical evidence and Delphi method of expert consultation and voting, 10 recommendations were put forward from two aspects of blood support mode and transfusion strategies, aiming to provide a reference for transfusion resuscitation in the emergency treatment of severe trauma and further improve the success rate of treatment of patients with severe trauma.