All 187 GCT samples from infected individuals were reactive by ELFA (Table ). Likewise, all GCT samples from noninfected individuals were negative. These results provided sensitivity and specificity values of 100% and positive and negative predictive values of 1 (P < 0.0001).
TABLE 1 Confirmation of ELFA reactivities by WB of GCTsamples
Detection of HIV antibodies in urine samples was positive by ELFA for 181 individuals (Table ). Of these, 178 were individuals with some stage of HIV infection (102 with CDC stage II infection, 19 with CDC stage III infection, and 57 with CDC stage IV infection), and 3 were noninfected individuals. Nine samples from seropositive individuals were negative by ELFA (four and five samples belonging to individuals with CDC stage II and IV infections, respectively). Of the 115 urine samples from seronegative persons, only 3 urine samples displayed reactivity by the ELFA technique (1 sample belonged to the donor group and the other 2 belonged to the group of individuals with high risk of HIV infection). These results yield a sensitivity of 95.2% and a specificity of 97.4%, with a positive predictive value and a negative predictive value of 0.98 and 0.93, respectively (P < 0.0001).
TABLE 2 Confirmation of ELFA reactivities by WB of urinesamples
The distribution of RFVs with GCT and urine samples can be seen in Tables and , respectively. It can be seen from the data in Table that 77% of the samples from seropositive individuals yielded an RFV of over 200, with no samples having values equal to or less than 10 RFVs. In Table it can be seen that only 24.1% of the urine samples from HIV-seropositive individuals had RFVs of >200, while 5.3% of the samples had negative RFVs (four samples from individuals with CDC stage II infection and five samples from individuals with CDC stage IV infection). On the other hand, the seronegative individuals displayed very similar RFVs: an RFV of 0 for 47.8% of GCT samples and 44.3% of urine samples and RFVs of between 1 and 10 for 52.2 and 54.9% for GCT and urine samples, respectively. Among the samples from noninfected persons, three urine samples were positive by ELFA, with RFVs in the range of 11 to 50.
TABLE 3 Distribution of RFVs for GCT samples from different populationgroups
TABLE 4 Distribution of RFVs for urine samples from different populationgroups
The average RFVs for GCT and urine samples from seropositive individuals were 1,946 ± 3,153 and 409 ± 980, respectively. Statistical comparison of the RFVs for samples from the HIV-infected groups did not show any significant differences between RFVs belonging to individuals with CDC stage II, III, and IV infections (Bonferroni’s test). This was true for both the GCT and the urine samples. However, significant differences were found between each of these HIV infection stages and the values obtained for noninfected groups.
The ELFA results were confirmed by WB. All GCT samples reactive by ELFA fulfilled the WHO criterion for positivity (Table ). In contrast, among the WBs performed with 190 urine samples, only 181 met the positivity criterion (96.8%) (Table ). The samples were distributed by stage as follows: 104 samples belonged to individuals with CDC stage II infection (2 samples were negative by ELFA), 19 samples belonged to individuals with CDC stage III infection, and 58 samples belonged to individuals with CDC stage IV infection (1 sample was negative by ELFA). The seven samples with negative WB results included two urine samples each from individuals with CDC stage II and IV infections (the samples were negative by ELFA), one sample from the blood donor group (the sample was positive by ELFA), and two samples from the group of individuals in a group at high risk of HIV infection (the samples were positive by ELFA). Finally, two samples with indeterminate WB results were found (the samples were from individuals with CDC stage IV infection) and had bands that were reactive to proteins gp160 and gp41, respectively (both samples were negative by ELFA).
The reactivity band most frequently observed by WB was the gp160 protein band (in 100% of GCT samples versus 97.3% of urine samples), and the least common reactivity band was the p17 protein band (in 31.5% of GCT samples versus 21.4% of urine samples) (Tables and ). The arithmetic mean of the observed number of bands was 6.7 for GCT and 6.5 for urine. Nevertheless, 23.2% of the WBs run with GCT samples showed all nine bands, while 32.2% of the WBs run with urine samples yielded five or fewer reactive bands. In the WBs with GCT proportion dropped to 25.5%.
TABLE 5 Reactivity patterns of GCT samples from HIV-infected individuals by WB forHIV
TABLE 6 Reactivity patterns of urine samples from HIV-infected individuals by WB forHIV
Only 1.6 and 0.5% of the WBs with GCT and urine, respectively, had the minimum WHO criterion for positivity, since the Western blots displayed only two bands, those for the envelope proteins (gp160 and gp120). In the Western blots with three bands (5.3% of GCT samples versus 6.4% of urine samples), in addition to the bands of reactivity to proteins gp160 and gp120, reactivity was observed to other proteins: gp41 (60% of GCT samples versus 50% of urine samples), p24 (20% of GCT samples versus 25% of urine samples), and p31 (20% of GCT samples versus 25% of urine samples).
Only WBs with urine samples displayed one reactive band (indeterminate WB results belonging to samples from individuals with CDC stage IV infection had two reactive bands to proteins gp160 and gp41, respectively).
Four reactivity patterns were observed for both types of samples: ENV (4.8% of GCT samples versus 4.8% of urine samples), ENV plus POL (11.2% of GCT samples versus 16.6% of urine samples), ENV plus GAG (4.8% of GCT samples versus 4.3% of urine samples), and ENV, POL, and GAG (79.2% of GCT samples versus 72.2% of urine samples).
Finally, Table gives the results from the ELFA analysis of the GCT and urine samples taken over a 24-h period from a group of six volunteers infected with HIV (CDC stage II infection). These results draw attention to the disproportionate RFVs between the RFVs found for GCT samples and their paired urine samples. In general, the RFVs for the GCT samples were always higher. The RFVs for samples subsequently obtained from each individual were similar. The same was true for urine samples. There seems to exist a certain parallel between the RFVs for GCT and urine samples from the same individual.
TABLE 7 Evolution of RFVs in GCT and urine samples over a 24-hperiod
The confirmation of the results by WB with GCT samples demonstrated that serial WBs displayed approximately the same intense bands. However, for urine samples, not only were the bands’ intensities less, but in some cases, some bands could be seen to be missing, even though they were present in the WBs performed with the respective GCT samples (Fig. ).
Reactivities observed by WB of GCT and urine samples from the same individual obtained over 24 h.