Resistance Tests ·
HIV reproduces rapidly in our bodies and in the process can produce variants of the virus that are resistant to some of the HIV drugs (ARVs) in use.
It’s important to know which of the drugs, if any, you are resistant to, as taking drugs that you are resistant to will result in HIV not being fully suppressed. This reduces the effectiveness of the drugs, increases the ability of HIV to damage the immune system, and can limit future treatment choices.
There are two types of resistance test, called genotype and phenotype.
The genotype test looks for typical changes in the genes of HIV that usually cause resistance. A genotype test is quicker to do and less expensive than a phenotype and will be the one you usually get unless you have particularly complex resistance patterns. Results generally come back within 2 weeks.
The phenotype test involves a sample of HIV from your blood being grown and tested in the laboratory against a variety of drugs. It takes a good while longer to come back from the lab, and is more expensive, but is useful if you have complex or unusual resistance patterns.
Resistance testing should be standard practice at first diagnosis, before starting therapy and whenever you have to change therapy as a result of treatment failure. If your clinic does not offer resistance tests, you should request them.
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