In this study, HIV-1 viral load quantitation determined by Nucleic Acid
Sequence Based Amplification (NASBA) was compared with other surrogate
disease progression markers (antigen p24, CD4/CD8 cell counts and b-2
microglobulin) in 540 patients followed up at Sao Paulo, SP, Brazil.
HIV-1 RNA detection was statistically associated with the presence of
antigen p24, but the viral RNA was also detected in 68% of the antigen
p24 negative samples, confirming that NASBA is much more sensitive than
the determination of antigen p24. Regarding other surrogate markers, no
statistically significant association with the detection of viral RNA
was found. The reproducibility of this viral load assay was assessed by
14 runs of the same sample, using different reagents batches. Viral
load values in this sample ranged from 5.83 to 6.27 log (CV = 36 %),
less than the range (0.5 log) established to the determination of
significant viral load changes