HIV Genotypic Resistance

Genotypic resistance assay

This blood test looks at the genetic makeup of a strain of HIV, the virus that causes AIDS.

If you are infected with HIV, this test may be done before you start taking antiviral medicine. It can help your healthcare provider figure out the best treatment to use. This helps because drug-resistant HIV strains continue to change.

The test can also help figure out if a medicine you are taking works for your type of HIV and if your virus has changed (mutated), in an effort to survive treatments. This test is only able to find known mutations.

You may need this test if your healthcare provider believes that the amount of HIV in your body is steadily increasing. This could happen even though you're taking antiviral medicines if you have a type of HIV that's resistant to treatment.

You may also have this test before starting HIV treatment. You might also be given this test if you are pregnant and need HIV medicines.

You may also need HIV phenotype resistance testing. But it takes longer to get the results for this test and the cost is higher. Also resistance measurements have not been set for all HIV medicines.

Test results may vary depending on your age, gender, health history, and other things. Your test results may be different depending on the lab used. They may not mean you have a problem. Ask your healthcare provider what your test results mean for you.

Test results include a combination of numbers and letters—for instance, K103N. Not all mutations of HIV resist medicine treatment, but some are commonly found in HIV.

This test may not find mutations that infect less than 20% of the virus population.  

The test is done with a blood sample. A needle is used to draw blood from a vein in your arm or hand. 

Having a blood test with a needle carries some risks. These include bleeding, infection, bruising, and feeling lightheaded. When the needle pricks your arm or hand, you may feel a slight sting or pain. Afterward, the site may be sore. 

Not taking your HIV medicines as prescribed can cause what may look like an error in your results (false-positive).

You don't need to prepare for this test. Be sure your healthcare provider knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illegal drugs you may use.