Figure 4: CD4% is plotted as the independent variable on the X-axis with the associated CD4 count plotted as the dependent variable on the Y-axis. A Becton-Dickinson FACSCanto II flow-cytometer in Boston tested 148 healthy and immunocompromised persons with CD4% ranging from 5% to 60%. The associated absolute lymphocyte counts above and below the American reference range (1,200 – 4,800 lymphocytes/microliter) are identified in orange. A total of 7% of samples were either above or below the reference range.