Clinical implications of identifying non-B subtypes of human immunodeficiency virus type 1 infection

Although human immunodeficiency virus type I (HIV-I) infection in the Unite d States has predominantly involved subtype B, increasing global travel is leading to wider dissemination of genetically heterogeneous subtypes, While physicians depend on HIV-1 viral load measurements to guide antiretroviral therapy, commonly used molecular assays may underestimate the viral load o f patients with non-B subtypes, Nine patients with non-B subtypes of HIV-1 were identified by physicians who suspected a non-B subtype on the basis of a low or undetectable HIV-I viral load, by the Amplicor HIV-1 Monitor test , version 1.0, in conjunction with either a declining CD4 cell count or his tory of travel outside the United States. Use of version 1.5 of the Amplico r HIV-I Monitor test detected a median HIV-1 viral load that was 2.0 log(10 ) RNA copies/ml higher than was determined with version 1.0, Clinical manag ement was altered in all eases after diagnosis of a non-B-subtype infection . These cases demonstrate that it is critical for physicians to suspect and diagnose non-B subtypes of HIV-1 so that an assay with reliable subtype pe rformance can be used to guide antiretroviral therapy.