Abstract
The Centers for Disease Control and Prevention has published laboratory guidelines for enumerating CD4+ T-cells from human immunodeficiency virus (HIV)-infected persons to help improve the quality of lymphocyte immunophenotyping. New data that clarify some of the variables in the process of immunophenotyping have been obtained. These include information relevant to both hematology and immunophenotyping procedures as well as quality control parameters that are important in producing reliable results.