Method and apparatus for screening obscured or partially obscured cells

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. The sensed characteristic of the white blood cell population subset of interest then is shifted by binding microspheres having monoclonal antibodies specific to the white blood cell population subset of interest to the cell population. The white blood cell population, and the standard population then are again counted and compared to the original counts to obtain an enumeration of the white blood cell population subset of interest.