Cyto-Chex BCT is a direct draw blood collection tube that maintains cellular morphology and surface antigen expression, including cluster of differentiation (CD) markers, prior to analysis by flow cytometry. Whole blood samples collected in Cyto-Chex BCT can be stored at room temperature for up to 14 days. Cyto-Chex BCT has been FDA 510(k) cleared for consistent recovery of HIV-associated lymphocyte subsets for up to 14 days.