Abstract:

Objective To investigate the value of the novel nasopharyngeal carcinoma（NPC） biomarker P85 antibody in screening high-risk individuals in low-incidence areas and its diagnostic efficacy for NPC. Methods A total of 156 high-risk patients（140 non-NPC and 16 NPC cases） were enrolled from Yueyang Hospital of Integrated Traditional Chinese and Western Medicine of Shanghai University of Traditional Chinese Medicine from January 2024 to December 2025. High-risk individuals were defined as those with positive plasma Epstein-Barr virus（EBV） DNA（≥400 copies·mL^-1） and positive serum EBV viral capsid antigen（VCA） IgA antibody and/or nuclear antigen 1（NA1） IgA antibody. The clinical data and EBV infection-related indicators（plasma EBV DNA load and serum EBV-related antibodies） were collected，and P85 antibody levels were determined. The diagnostic efficacy of each indicator for NPC was evaluated using receiver operating characteristic（ROC） curve. To avoid overfitting in small samples，5 cross-validation methods（K-fold，leave-one-out，leave-group-out，bootstrap and stratified K-fold） were used to internally validate the diagnostic efficacy，and the corrected area under curve（AUC） and 95% confidence interval（CI） were calculated. Results The serum P85 antibody level in NPC group was higher than that in control group（P<0.001），while there was no statistical significance in plasma EBV DNA load，NA1 IgA antibody and VCA IgA antibody levels between the 2 groups（P>0.05）. The AUC for diagnosing NPC by EBV DNA，NA1 IgA antibody，VCA IgA antibody and P85 antibody were 0.514，0.587，0.633 and 0.916，respectively. After validation by 5 cross-validation methods（K-fold，leave-one-out，leave-group-out，bootstrap and stratified K-fold），the corrected AUC of P85 antibody were 0.879，0.874，0.919，0.910 and 0.898，respectively，with small fluctuations among different methods. The AUC of EBV DNA，NA1 IgA antibody and VCA IgA antibody ranged from 0.543 to 0.770，0.542 to 0.860 and 0.482 to 0.654，respectively，with large fluctuations among different methods. Conclusions P85 antibody has high specificity in high-risk individuals in low-incidence areas of NPC and can be used as a novel diagnostic marker for NPC in such areas.

Key words: P85 antibody, Epstein-Barr virus, Nasopharyngeal carcinoma, High-risk population, Cross-validation