The investigators intend to test Epstein-Barr virus antibodies (Viral Capsid Antigen-immunoglobulin A， Epstein-Barr nuclear antigen 1-immunoglobulin A， early antigen-immunoglobulin A， Zta-immunoglobulin A， Rta-immunoglobulin G, Bnlf 2b) by ELISA and Epstein-Barr virus DNA by quantitative polymerase chain reaction, target sequencing and CRISPR-associated protein 12a in nasopharyngeal brushing and plasma of the same population at high-risk of nasopharyngeal carcinoma so as to determine the best method in nasopharyngeal carcinoma screening.
The investigators intend to compare Epstein-Barr virus antibody and Epstein-Barr virus DNA screening efficacy in first-degree relatives of nasopharyngeal carcinoma patients.