We have all heard of the problems HIV resistance can cause. It can render a therapy regimen virtually useless. But what exactly is resistance testing and how to HIV specialists use resistance testing when treating the HIV positive patient.
Genotype assays
This test examines viral genetic material and identifies particular mutations responsible for resistance. Generally the viral load needs to be above a certain value, i.e. greater than 1000 copies/mL, in order for genotype testing to be of any use. If genotype testing reveals a mutation known to cause resistance to a particular drug, then an alternative therapy and drug choice must be considered.
Phenotype assays
This test measures the ability of the virus to grow and replicate in the presence of varying concentrations of drugs. A virus that grows well in the presence of even a high concentration of drug is a sign of resistance to that drug.
