Abstract: A method for performing screening of one or more cell groups of interest obscured by a cell population such as one or more subsets of interest of a WBC population utilizing at least one light sensing parameter. The cell group of interest is enumerated by utilizing microspheres having monoclonal antibodies bound thereto to modify the sensed characteristics of specified cells to differentiate the cell group of interest from the obscuring cell population.

Abstract: A method and apparatus for performing screening of obscured or partially obscured cells to enumerate one or more cell population subsets. For example, a whole blood sample or portion thereof is screened to provide the desired analysis of one or more white blood cell population subsets in the sample. A white blood cell population including the obscured subset of interest is first counted, along with a standard population. The standard population can be one of the total number of white blood cell populations, a second white blood cell population which does not obscure the shifted or non-shifted sensed characteristic of the subset of interest, an artificial population formed by microspheres which also do not obscure the shifted or non-shifted sensed characteristic of the subset of interest or a white blood cell population into which the sensed characteristic of the subset will be wholly or partially shifted.