What it measures: Whether you have a gene that marks you as allergic to Ziagen (abacavir)—a potentially serious side effect in 5 percent of positive people using the drug
When it’s used: If you’re considering Ziagen
What it shows: Whether you should steer clear of abacavir in any of its forms, including Ziagen, Trizivir, and Epzicom
What it measures: Whether you have the so-called CCR5-tropic virus. Selzentry (maraviroc) and other CCR5 inhibitors work against only this strain of HIV.
When it’s used: If you’re considering Selzentry (maraviroc)
What it shows: If you have the “right kind” of virus (CCR5-tropic), this new drug may work for you. If you don’t, you’ll need to consider other options. So far, maraviroc is only for people resistant to most other HIV medications. If you’re newer to treatment and have other options, you won’t need to worry about the tropism test.