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Two hundred and ten subjects with HIV-indeterminate WB results were detected from 6360 positive samples obtained via HIV screening received confirmatory HIV testing in Fujian Province between 2015 and 2016. The proportion of HIV-indeterminate WB results was 3.3% (210/6360). There was a significant difference in the proportion of HIV-indeterminate WB tests among different populations (χ2 = 122.098, P < 0.001) (Fig. 1), with the highest being recorded for pregnant and lying-in women receiving physical examinations (16.67%, 22/132), followed by that for voluntary blood donors (8.82%, 30/340).
Figure 1. Detection of HIV-indeterminate Western blot results among different subject populations. Others include the spouse or sexual partner of HIV-positive patients, the children HIV-positive women, those with professional exposure, entertainment workers, paid blood donors, entry-exit personnel, recruits and those enrolled in ad hoc surveys.
The HIV-indeterminate WB samples were mainly derived from other clients (32.86%), preoperative examinations (17.62%), and VCT (17.14%) (Fig. 2). The 210 subjects with HIV-indeterminate WB results comprised 142 men (67.62%) and 68 women (32.38%) who had a mean age of 39.95 ± 17.70 years. Of these 210 individuals, 112 (53.33%) reported no high-risk sexual behaviors, one (0.48%) was a child delivered by an HIV-infected woman, and 97 (46.19%) reported high-risk sexual behaviors (64.95% heterosexual behavior and 35.05% homosexual behavior). All subjects stated that they had not received ART during the first blood sampling after enrollment.
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A total of 16 WB band patterns were detected among the 210 HIV-indeterminate WB samples, the three most common patterns of which were a single p24 band (44.29%), a doublet of gp160 and p24 (17.62%) bands, and a single gp160 band (14.29%) (Table 1).The Env protein showed 10 banding patterns in 98 HIV-indeterminate WB samples (46.67%), the Gag protein showed three patterns in 107 samples (50.95%), and the Pol protein showed three patterns in five samples.
Type of HIV protein Western blot band pattern No. subjects No. subjects receiving follow-up Follow-up outcomes No. of negative HIV antibodies No. of positive HIV antibodies No. of indeterminate HIV antibodies Env gp160 30 26 19 6 1 gp160 + p24 37 29 2 25 2 gp160 + gp120 9 7 2 4 1 gp160 + gp120 + gp41 15 6 0 4 2 gp160 + p24 + p17 2 2 0 2 0 gp160 + p55 + p51 1 1 1 0 0 gp160 + p66 + p51 + p24 1 1 0 1 0 gp120 1 0 0 0 0 gp41 1 1 1 0 0 gp41 + p24 1 1 1 0 0 Total 98 74 26 42 6 Gag p24 93 71 57 11 3 p24 + p17 4 3 3 0 0 p17 10 6 5 0 1 Total 107 80 65 11 4 Pol p51 3 1 0 1 0 p66 1 1 1 0 0 p66 + p51 1 1 1 0 0 Total 5 3 2 1 0 Total 210 157 93 54 10 Table 1. Western blot band patterns and follow-up outcomes in patients with HIV-indeterminate Western blot results.
There were 157 subjects with HIV-indeterminate WB results receiving follow-up until June 2017, which represented a follow-up rate of 74.76%, and the positive and negative conversion rates were 34.39% (54/157) and 59.24% (93/157), respectively. In addition, there were 10 samples (6.37%) for which indeterminate results were still obtained after a 6-month follow-up (Table 1).
Among samples with the common WB band patterns, the highest negative conversion rate of HIV antibodies (80.28%, 57/71) was seen in samples with a single p24 band, followed by that in samples with a single gp160 band (73.08%, 19/26). In contrast, the highest positive conversion rate (86.21%, 25/29) was found in samples with the doublet of gp160 and p24 bands. In addition, the highest negative conversion rate of HIV antibodies (81.25%, 65/80) was detected in samples with a Gag band, whereas the highest positive conversion rate (56.76%, 42/74) was seen in samples with an Env band (Table 1).
When we examined the seroconversion outcomes of HIV antibodies in patients with a different number of WB bands, we detected positive conversion rates of 16.98% (18/106), 70.73% (29/41), and 70% (7/10) in subjects with a single WB band, two bands, and three and more bands, respectively (Table 2). Trend analysis using a Chi square test revealed an increase in the possibility of a positive HIV antibody conversion with an increase in the number of WB bands (χ2 = 45.71, P < 0.001).
Western blot band pattern No. subjects No. subjects receiving follow-up Follow-up outcomes No. of negative HIV antibodies (%) No. of positive HIV antibodies (%) No. of indeterminate HIV antibodies Single band 139 106 83 (78.30%) 18 (16.98%) 5 Double bands 52 41 9 (21.95%) 29 (70.73%) 3 Three bands or more 19 10 1 (10%) 7 (70%) 2 Total 210 157 93 54 10 Table 2. Follow-up outcomes for HIV-indeterminate western blot samples with different numbers of Western blot bands.
We subsequently examined the seroconversion outcomes of HIV antibodies in different categories of patients with HIV-indeterminate WB results. We accordingly found that the negative conversion rate was 100% (19/19), 86.86% (20/23), and 73.08 (19/26) in pregnant and lying-in women receiving physical examinations, voluntary blood donors, and preoperative examinees, whereas the positive conversion rate of HIV antibodies was 53.33% (16/30) and 58.54% (24/41) in VCT and other clients, respectively. Furthermore, we detected a significant difference in the seroconversion outcomes of HIV antibodies among the different categories of patients with HIV-indeterminate WB results (χ2 = 30.212, P < 0.001).
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A total of 157 individuals with HIV-indeterminate WB samples were successfully followed up, including sample from 54 individuals with positive conversion of HIV antibodies, 93 samples with negative conversion, and 10 samples with indeterminate WB results. Among the different assays assessed, quantitative HIV nucleic acid testing showed the highest sensitivity (96.3%, 52/54), followed by qualitative HIV nucleic acid testing (94.44%, 51/54). The lowest sensitivity (42.59%, 23/54) was obtained with p24 antigen detection. In terms of specificity, qualitative HIV nucleic acid testing was found to be the most specific (97.85%, 91/93), followed by p24 antigen detection (96.77%, 90/93). Lowest specificity (90.32%, 84/93) was obtained using quantitative HIV nucleic acid testing. The highest coincidence rate was obtained with qualitative HIV nucleic acid testing (96.6%, 142/147), followed by quantitative test (92.52%, 136/147), and was lowest (76.87%, 113/147) with p24 antigen detection (Table 3).
Western blot P24 antigen detection Quantitative HIV nucleic acid test Qualitative HIV nucleic acid test Total + - + - + - + 23 (42.59%) 31 (57.41%) 52 (96.3%) 2 (3.7%) 51 (94.44%) 3 (5.56%) 54 - 3 (3.23%) 90 (96.77%) 9 (9.68%) 84 (90.32%) 2 (2.15%) 91 (97.85%) 93 Total 26 121 61 86 53 94 147 Table 3. Performance of different assays for the differential diagnosis of HIV-indeterminate Western blot samples.