Significance of Specific Epstein‐Barr Virus IgA and Elevated IgG Antibodies to Viral Capsid Antigens in Nasopharyngeal Carcinoma Patients

The feasibility of using elevated Epstein‐Barr virus (EBV) specific‐IgG antiviral capsid antigen (VCA) and IgA anti‐VCA antibody levels as an aid in diagnosis of nasopharyngeal carcinoma (NPC) was analyzed by determination of serum anti‐body titers to EBV in 54 NPC patients, 114 healthy blood donors, and 40 family members by the immunoperoxidase assay (IPA). No significant difference was found in the prevalence rate of EBV IgG anti‐VCA antibodies (titer ≥20) between the patient group and the control and family groups (100% vs 92% and 90%, respectively). The prevalence rate of elevated EBV IgG anti‐VCA titers (≥ 80, ≥ 160, ≥ 320, and≥ 640) was significantly higher in the NPC patients than in controls. For example, at an IgG titer of ≥320, the prevalence rate was 82% in the NPC patient group and 1.7% in the controls (P <0.0001). The prevalence of EBV IgA anti‐VCA antibodies (≥ 10) was significantly higher in the NPC patients than in control and family groups (82% vs 6.1% and 0%, respectively). The prevalence rate for elevated EBV IgA anti‐VCA (≥20) was found to be significantly higher (P <0.0001) in NPC patients than in the control group (70% vs 1.7%). A significantly high proportion (P = 0.0004) of NPC patients who had serum EBV IgA anti‐VCA titers of <20 had elevated IgG titers to VCA ≥ 320 (21 % vs 1.7% among controls). It appears that testing for IgG antibodies at a serum dilution of 1:320 and for IgA antibodies at a dilution of 1:20 by the IPA technique comprises the best combination for the differentiation between NPC patients and health controls (91% vs 3.4%), and it is suggested that these be used as screening markers for NPC patients.