Methods, systems, and computer program products for the analysis of particle analyzer data are disclosed. One embodiment is a method of analyzing immature reticulocytes in a blood sample, including the steps of: preprocessing the blood sample; measuring the blood sample by a detection including a reticulocyte-maturity measurement and a light scatter measurement; analyzing blood cell distribution patterns to identify a set of reticulocyte events; differentiating immature reticulocytes from mature reticulocytes using the reticulocyte-maturity measurement and the light scatter measurement; and reporting immature reticulocytes. The immature reticulocyte fraction may be one aspect that is reported. Also another method is disclosed, having the steps of: measuring the blood sample by a detection comprising an axial light loss measurement; identifying a hard-to-ghost cell population based on the axial light loss measurement; filtering-out the hard-to-ghost cell population; and analyzing the event data to identify blood cell distribution patterns.