HIV: Treatment, reduction of the viral load

The viral load is measured with various techniques such as quantitative PCR (HIV RNA or bDNA, branched DNA) and is expressed as the number of viral RNA copies per millilitre of blood. Combination antiviral treatment with at least 1 protease inhibitor reduces the viral load in 80% of treated patients to below the present detection limit. However, it is still not yet known how long this effect lasts. A viral load of >30,000 copies of RNA/ml is often regarded as an indication for antiviral drug therapy. A drug is considered effective when a reduction of at least 90% of the initial viral load can be achieved. It is of course best to achieve an undetectable viral load. Most current techniques have a detection limit of 50 RNA copies per ml. The question to what extent the viral load in the blood reflects the viral load in various tissues has not yet been satisfactorily answered. Some HIV strains are difficult to detect with the currently available commercial techniques.