A new viral load test can detect HIV at even lower levels
A new generation test system, known as Cobas 6800, has a lower virus detection limit. The system uses polymerase chain relation (PCR) analysis aimed at two different areas of the HIV genome (gag and LTR). The article was published in POZ magazine.
HIV viral load is considered undetectable when it falls to somewhere between 20 to 50 copies, but some tests used around the world might not be able to track the virus accurately at such low levels.
Researchers at the Sorbonne Université in Paris estimated the difference between the widely used Cobas AmpliPrep/COBAS TaqMan system to the newer Cobas 6800 system.
The research team selected two groups of people living with HIV:
- Group 1: 200 people with a viral load below 50 copies for at least three years.
- Group 2: 35 people who were periodically diagnosed with low-level viraemia.
When testing was switched to the Cobas 6800 system the researchers discovered that 25% of people in group one who were previous considered undetectable had a detectable level of virus. In group one more people had a viral load between 20-50 copies on Cobas 6800 (37%) compared to the older test (19%). In group two every participant showed a detectable result on the newer system (100%) compared to the older test (66%).
These findings have raised some concerns about “undetectable = untransmittable” or “U=U”. However, researchers and HIV advocates have pointed out the scientific basis for the U=U statement is based on multiple studies that used a viral load of less than 200 copies. This has lead to a new slogan “199 or below, good to go.”.
