This is a multi-center study designed to assess the accuracy of Pima™ CD4 Test to enumerate CD4+ T-cells in whole blood over the measurement range expected for the intended population. The Pima CD4 Test consists of the Pima™ CD4 cartridge and Pima™ Analyzer to identify and determine the absolute counts of mature helper (CD3+/CD4+) T-lymphocytes in whole blood.