Establishment of Diagnostic Criteria Using EBNA1 IgA Antibody Levels in a High-Risk Area for Nasopharyngeal Carcinoma

摘要

OBJECTIVE The EBNA1 IgA antibody level of normal and NPC subjects in a high incidence area were analyzed for new diagnostic criteria to improve diagnosis. METHODS A total of 780 normal and 104 NPC sera were tested for EBNA1 IgA antibody levels by ELISA. Two diagnostic criteria were obtained from sensitivity and specificity data: 1) lower equivocal limit (rOD = 1.10) where sensitivity = 95%; and 2) upper equivocal limit (rOD = 1.85) where specificity = 95%. RESULTS The range and distribution of EBNA1 IgA antibody levels are broad with those of normal subjects (0.093 - 4.726, mean = 0.850 ± 0.637) overlapping those from NPC subjects (0.235 - 3.721, mean = 2.241 ± 0.875). However, NPC subjects did exhibit significantly higher antibody levels (t = 18.5, P < 0.001). Based on the diagnostic criteria, 3 diagnostic categories were established: ① Positive; ② Suspected Positive; and ③ Negative. The percentage of NPC subjects falling into these 3 diagnostic categories were 75.13%, 17.44% and 7.44%, respectively and of normal subjects, 4.81% , 17.31%, 77.88% respectively. CONCLUSION Due to the broad distribution and overlapping of antibody levels between normal and NPC subjects in a high incidence area, it is important to have diagnostic criteria that will categorize those with equivocal results to minimize misdiagnosis. The 3 diagnostic categories established in this study will enhance detection and help physicians in their clinical diagnosis.