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.
