[Study on the indeterminate results of characterization and verification of HIV antibody from Western blot test]

To study the serological characterization of indeterminate Western blot (WB) results of HIV antibody and to find a new way to verify the HIV antibody indeterminate results and provide references for editing "National Guideline for Detection of HIV/AIDS".

All of the 42 subjects who were confirmed as indeterminate HIV antibody in People' Liberation Army HIV Confirmation Laboratory from 2005 to 2006, were collected. Line immunoassay, HIV viral load test and HIV-1 p24 were tested and followed up for 3-6 months' to compare the changes of WB bands patterns.

(1) For the 42 individuals with indeterminate HIV antibody, a total of 8 different patterns of bands were found in WB test including 45.2% of them were p24 mono band, 30.9% were gp160 mono band, 11.9% were gp160 with p24, 2.4% (only one case) were gp160gp120 +/-, gp41p24, p24p17, gp41 or gp120 respectively. It was noticed that the most patterns of common bands with indeterminate results were p24 mono band, gp160 mono band and gp160 with p24, which composed 88.0% of the whole indeterminate WB band patterns. (2) Twenty three cases had been followed up for more than 3 months with 22 giving no WB band image change and were confirmed as HIV sero-negative. The other one with case gp160 and p24 had developed to more bands in the period of 77 days follow-up with more bands, including gp160, gp120, p66, p31, p24 and p17,showed up and was confirmed as HIV primary infection. (3) Line immunoassay was applied to all of those 23 cases who had been followed up and the results showed that only one serological change was found and the case was confirmed to be HIV-positive. Among the other 22 cases without serological changes, 16 cases were proved to be HIV-negative, 6 cases were still indeterminate. The specificity was 72.7%. P24 antigen test showed negative in all the 23 cases, including the case which later was confirmed as HIV-positive. Of all the 23 originally indeterminate cases, viral loads were tested in 7 cases. Positive result was found in the case which was proved later to be HIV-positive. No viral loads were detected in the other 6 cases (< LDL).

The most common band patterns of indeterminate HIV antibody were mainly p24 monoband, gp160 monoband or with p24. Most of them (95.6%) were not infected by HIV, the bands showed up in WB test and demonstrated as non-specific reactions. Line immunoassay could determine about 70% of the indeterminate reactions. Results from viral load test also suggested that it was an efficient method to discriminate indeterminate results. With these two techniques, HIV serology could be diagnosed without 3 months' follow-up in primary infection which gave indeterminate WB results.