The ADVIA graphically represents the internal complexity of red blood cells (equivalent to the cellular hemoglobin or CH) of each individual red blood cell in a histogram, while accounting for the optically measured volume of each individual red blood cell, i.e. HC or hemoglobin concentration = CH/volume for each cell. The histogram represents the distribution of red blood cell hemoglobin concentration or HC, ranging from 0 to 50 g/dL. It demonstrates small populations of cells with high (hyperchromic) or low hemoglobin (hypochromic) content, even before there are changes in the mean hemoglobin concentration (CHCM or MCHC). For example, in early iron deficiency, a second population of red blood cells with low hemoglobin (hypochromic) may be seen to the left of the general population of red blood cells that contain normal amounts of hemoglobin (normochromic) before any changes in mean hemoglobin concentration are evident. Increases in hemoglobin concentration (hyperchromic) is usually an artifact, e.g. from excess EDTA drawing water out of the cells and causing cell shrinkage.
