Diagnostic Performance of Anti–Epstein-Barr Virus BNLF2b in Suspected Nasopharyngeal Carcinoma

Importance: It remains uncertain which Epstein-Barr virus (EBV)-related biomarkers provide the most reliable diagnostic performance for suspected nasopharyngeal carcinoma (NPC) in outpatient settings, especially regarding the novel anti-EBV BNLF2b total antibody (P85-Ab) assay. Clarifying their accuracy is critical to improving early detection and reducing misdiagnosis. Objective: To evaluate the diagnostic performance of the P85-Ab assay in suspected NPC in outpatient settings and compare it head-to-head with EBV viral capsid antigen (VCA)-immunoglobulin A (IgA), EBV early antigen (EA)-IgA, and EBV nuclear antigen 1 (EBNA1)-IgA. Design, Setting, and Participants: A prospective, multicenter cohort study was conducted between April 2021 and March 2024, with a median follow-up of 27.2 months in outpatient clinics across 5 medical centers in China. Key inclusion criteria comprised clinically suspected NPC. Data were analyzed from June 2025 to July 2025. Exposures: P85-Ab was tested using chemiluminescent immunoassay. VCA-IgA, EA-IgA, and EBNA1-IgA were tested via enzyme-linked immunosorbent assays. Main Outcomes and Measure: Primary outcomes included sensitivity and specificity of P85-Ab. Results: A total of 3795 eligible participants were consecutively recruited. After excluding individuals with low-quality samples or lost to follow-up, 3777 participants were included in the final analysis (1680 with NPC and 2097 without NPC). Among the 3777 evaluated participants (median [IQR] age, 49.0 [37.0-58.0] years; 65 % male), P85-Ab demonstrated superior diagnostic performance, with a sensitivity of 93.0% (95% CI, 91.6-94.0) and specificity of 97.3% (95% CI, 96.5-97.9). Other biomarkers showed lower sensitivity (ranging from 60.4% to 93.0%) and specificity (<90%). P85-Ab maintained high sensitivity among asymptomatic individuals (92.0%; 95% CI, 85.9-95.6) and those presenting with NPC-nonspecific symptoms (88.4%; 95% CI, 75.5-94.9), with no additional diagnostic benefit observed from the triplet-antibody strategy combining P85-Ab, VCA-IgA, and EBNA1-IgA. However, among participants with NPC-specific symptoms, the triplet-antibody strategy improved sensitivity compared with P85-Ab alone (95.9%; 95% CI, 94.8-96.8 vs 93.1%; 95% CI, 91.7-94.3; P < .001). Conclusions and Relevance: In this cohort study, P85-Ab was a robust and accurate biomarker for suspected NPC in outpatient settings. P85-Ab alone may be suggested for populations with asymptomatic or NPC-nonspecific symptoms, and combining P85-Ab with VCA-IgA and EBNA1-IgA may be suggested for populations with NPC-specific symptoms.