Genotypic resistance to d4T is not readily identified. Until a less costly and more widely available phenotypic assay is developed, healthcare providers are limited to the information that genotypic testing provides. This information may only be as good as an accurate history of a patient's prior antiretroviral therapy. The genotypic assay's main utility is in identifying drugs that will not be effective against the viral strains in a particular person. A three-fold increase in viral load is generally accepted as an indicator that antiretroviral therapy is failing.
Genotypic testing does have significant limitations.
The treatment information suggested by the genetic mutations that the assay reveals is not conclusive, and the LiPA HIV-1 RT test only identifies possible HIV resistance to nucleoside analogs, not possible future treatment options. It can take hold at many sites in the body, but it most commonly occurs in the gastrointestinal system, where it can cause severe digestive problems, and in the eyes, where it can cause blindness. The researchers conclude that regular use of condoms can prevent CMV infection in HIV-positive men. Because CMV is so widespread, most people with HIV already have it when they are diagnosed. Prophylaxis can sometimes prevent illness in CMV-infected individuals with very low CD4 counts.