With the ADVIA hematology analyzer, red blood cells (RBC) are flowed individually through a laser light in a flow cell. As the RBC passes through the light, it scatters the light in a forward (low angle) direction and in a side (high angle) direction. The degree of forward scatter is measured as the cell volume, as depicted here (larger cells scattering more light than smaller cells), whereas the degree of side scatter is equivalent to the cellular hemoglobin content in pg (cells with less hemoglobin would scatter less light in the side direction). The ADVIA then compiles the results of the individual RBC hemoglobin content per unit volume (cellular hemoglobin divided by volume) as a histogram (RBC HC), where the number of cells is shown on the Y-axis and the hemoglobin concentration (g/dL) is shown on the X-axis (ranges from 0-50 g/dL). The CHCM result provided by the analyzer is the mean of the cellular hemoglobin concentrations. Thus, the CHCM takes into account volume and is a concentration, whereas the CH does not (content only)
