A review paper suggesting a strategy for interpretting non-specific and non-standardized HIV tests:
The signal/cut-off ratio in any assay has no predictive value for the signal/cut-off ratio in any other assay, since the signal/cut-off ratios do not correlate for any of the
investigated ELISA pairs (Figure 1).
On the other hand, all sera with a signal/cut-off ratio greater than 2.0 for all ELISA pairs were also positive in Western blot. This fact was used to develop a simplified confirmation strategy for HIV testing (Figure 2).
ie – ‘HIV positive’ is when a group of different tests can be made to have some sort of internal agreement with each other, above a particular cut-off line. What does it actually mean? That’s a good question. One thing that it can not be said to mean is that the tests have any one particular meaning or reaction.