Enhancing the efficiency of Epstein-Barr viral serologic test in the diagnosis of nasopharyngeal carcinoma.

OBJECTIVE: To investigate the efficiency of concurrent application of VCA-IgA, EA-IgA and EA-IgG serological tests in diagnosing nasopharyngeal carcinoma (NPC). METHODS: The sera of 266 untreated NPC patients and 347 healthy adults were collected. In addition to the conventional immunoenzymatic method of VCA-IgA test, enzyme-linked immunosorbent assay (ELISA) was adopted as an alternative to test the antibody level of EA-IgG and EA-IgA. A new statistical formula was used to evaluate the odds ratio of different combinations of these three tests. RESULTS: The sensitivity and specificity of VCA-IgA, EA-IgG and EA-IgA concurrently were as high as 95.11% and 97.41%, respectively, which were higher than those of single test (90.60% and 94.52% for VCA-IgA, 93.98% and 93.66% for EA-IgG, 89.84% and 88.18% for EA-IgA). Furthermore, the odds ratio of 3-test positivity (1 912.5) was higher than those of 2-test positivity (27.903 2 for VCA-IgA and EA-IgG, 11.169 0 for EA-IgG and EA-IgA, 8.032 8 for VCA-IgA and EA-IgA), which were even higher than those of 1-test positivity (0.121 4 for VCA-IgA, 0.170 5 for EA-IgG and 0.048 8 for EA-IgA). CONCLUSION: ELISA is more accurate in reflecting the antibody level of EA-IgG and EA-IgA than the conventional immunoenzymatic method. The concurrent application of VCA-IgA, EA-IgG and EA-IgA test can markedly improve the sensitivity, specificity and odds ratio as well, thus resulting in enhancing the efficiency of diagnosing nasopharyngeal carcinoma serologically.

[Value of EBNA1-IgA and EA-IgG in serological diagnosis of nasopharyngeal carcinoma].

OBJECTIVE: To evaluate the value of EBNA1-IgA and EA-IgG in serological diagnosis of nasopharyngeal carcinoma (NPC). METHODS: The serum EBNA1-IgA and EA-IgG of 56 patients with NPC and 58 healthy adults were detected by ELISA. The sensitivity, specificity, positive predictive value, accuracy rate and odds ratio of the two tests used singly or in combination were compared with each other. RESULTS: The sensitivity of EBNA1-IgA (91.07%) was higher than that of EA-IgG (87.50%), while the specificity of EA-IgG (87.93%) was higher than that of EBNA1-IgA (84.48%). The combination of EBNA1-IgA and EA-IgG could enhance the specificity (94.83%), positive predictive value (0.9375), likelihood ratio (15.5435) and odds ratio (75.0000) for serological diagnosis of NPC. Forty-five patients showed both positive EBNA1-IgA and positive EA-IgG. A positive EA-IgG was detected in 4 out of 5 patients with negative EBNA1-IgA and a positive EBNA1-IgA was founded in 6 out of 7 patients with negative EA-IgG. CONCLUSION: Although relatively high sensitivity and specificity could be obtained by either EBNA1-IgA or EA-IgG test alone, the combination of these two tests with a complementary effect is able to enhance the reliability of serological diagnosis of NPC as most patients have positive ENBA1-IgA and EA-IgG concurrently.

[Screening of dominant epitopes of antigens related to antibodies in the sera of patients with nasopharyngeal carcinoma].

BACKGROUND & OBJECTIVE: Epstein-Barr virus (EBV) is closely related to nasopharyngeal carcinoma (NPC). Many kinds of methods can be used to examine antibodies in NPC patients sera. This study was to screen the dominant epitopes from random peptide libraries (RPLs) displayed on phage using the EBV-related antibodies purified from the sera of NPC patients, and find new antigens at the epitope level. METHODS: The EBV-related antibodies were eluted from the sera of NPC patients using B95-8 cell EBV proteins as antigen, and the phages from 12-mer RPLs were elutriated for 3 rounds with the antibodies. The positive clones were gained by sandwich ELISA, and competitive inhibition assay from the third elution. The positive clones were sequenced, and the peptide coded by the inserted DNA were blasted with the antigen region of EBV proteins. RESULTS: Sixty-four phage clones were randomly picked up from the third eluate,25 positive clones were picked up using sandwich ELISA assay, the positive percentage was 39.06%. Thirteen clones were picked up for competitive ELISA assay,11 clones showed inhibitory phenomena,the inhibitory rates were between 18.09% and 65.94%. Five positive clones with high absorbency value, and high inhibitory rates were selected out, the sequences of peptides displayed on these clones were -A-T-S-H-L-H-V-R-L-P-W-T- (d15, and d18), -G-S-T-H-K-H-N-H-F-N-K-T- (d19), -K-P-I-H-E-H-P-H-R-F-K-S- (e8), -H-T-H-K-I-K-I-P-L-P-I-Q- (e23). These peptide sequences showed similarity with the amino acid sequences located in antigen regions of EBV integral membrane protein (d15, and d18), EBV thymidine kinase (d19), and EBV major capsid protein (e8, and e23). CONCLUSION: EBV-related epitopes could be obtained by screening the phages from RPLs with polyclonal antibodies purified from the sera of NPC patients, which may offer new methods of antigen preparation for sera diagnosis of NPC.