血清EB病毒抗体EBNA1 IgA检测临界值探讨

The Discussion on Determination of the Critical Value for EBNA1 IgA Antibody Level in Serum

目的:通过对健康人群与鼻咽癌患者EB病毒抗体EBNA1IgA水平的分析,探讨在鼻咽癌高发区应用该抗体作为鼻咽癌血清学指标时临界值的确定。方法:采用ELISA法检测780例健康人和104例鼻咽癌患者血清EB病毒EBNA1IgA,根据灵敏度和特异度曲线分别选择灵敏度、特异度在95%所对应的rOD值作为阴性临界值和阳性临界值,根据该临界值将人群划分成3个不同等级,rOD≥1.85为阳性,1.85>rOD≥1.10为可疑阳性,rOD<1.10为阴性。结果:健康人群EBNA1IgA的均值是0.850±0.637,鼻咽癌患者为2.241±0.875。健康人群中EBNA1IgA阴性、可疑阳性和阳性人群分别占75.13%、17.44%和7.44%,而鼻咽癌患者则分别是4.81%,17.31%,77.88%。结论:鼻咽癌高发区人群血清EBNA1IgA的rOD值离散程度较大。以EBNA1IgA作为鼻咽癌血清学诊断指标,可根据灵敏度和特异度确定阳性、可疑阳性和阴性3个人群,以利于临床作出对鼻咽癌的辅助诊断。

Objective: To analyze the EBNA1 IgA antibody level of normal and NPC subjects in high-risk area for new diagnostic criteria to improve diagnosis. Methods: EBNA1 IgA antibody levels of 780 normal and 104 NPC sera were tested using ELISA. Two diagnostic criteria were obtained from sensitivity and specificity data: a) lower equivocal limit (rOD=1.10) where sensitivity was 95%; b) upper equivocal limit (rOD=1.85) where specificity was 95%. Results: The range and distribution of EBNA1 IgA antibody levels were 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, the antibody levels was significantly high in NPC subjects (t=18.5, P<0.001). Based on the diagnostic criteria, three diagnostic categories were established: 1) Positive; 2) Doubtfully positive; and 3) Negative. Percentage of NPC subjects falling into the three diagnostic categories was 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 the area of high incidence, it is important to have diagnostic criteria that will categorize those with equivocal results to minimize misdiagnosis. The three diagnostic categories established in this study will enhance the detection and will be beneficial for physicians in their clinical diagnosis.