Stanford University School of Medicine's researchers recently put together a list of 93 common mutations of the AIDS virus, which can be associated to its drug resistance.
The researchers, who carried out this work in collaboration with the World Health Organization and seven other laboratories, say that the list can be used to track future resistance trends throughout the world.
They revealed that they analysed data from about 15,220 patients across the globe to develop an updated and accurate list of the most common, resistance-related mutations of the virus.
"The epidemic is changing, especially as new drugs are being developed," said Dr. Robert Shafer, associate professor of infectious diseases and geographic medicine at Stanford and the senior author of the paper.
"To effectively track the spread of drug resistance, particularly transmitted drug resistance, you need a sensitive and specific list that's considered standard and is adopted by all the surveillance studies," he added.
He further said that the list, published online in the journal PLoS-One, is important because it helps countries gauge the effectiveness of their HIV medication programs.
In 2007, Shafer and his colleagues published a similar list of 80 HIV mutations, which that has since served as the basis for global AIDS surveillance work.
The researchers said that with the scale-up of antiretroviral drug programs in the last two years and the introduction of new medications, resistance patterns have changed, which is why there was a need for a newly updated reference.
For compiling the latest list, the researchers added data from other laboratories in Europe, Canada and the United States to include more than 15,000 sequences from untreated individuals, double the number available in 2007.
They scoured the data to ensure they included only those mutations that were clearly recognized as causing or contributing to resistance, and excluded variants of the virus that can arise naturally as well as drug-related mutations that occur rarely.
The result was that 16 new mutations were added to the 2007 list, while three were dropped.
Shafer said that it was reassuring to find minimal changes were needed.
"It shows the first list was quite good," he said.