A biometrical view on normal values of CD4 and CD8 lymphocyte counts in peripheral blood

Statistical methods have been used to determine an optimal approach to the definition of the reference range for CD4 ("helper") and CD8 ("suppressor/cytotoxic") T cell numbers and the CD4/CD8 ratio in the peripheral blood. A graphical presentation of the absolute values for CD4 and CD8 for 85 healthy blood donors showed that a reference ellipse defined by fitting a gaussian distribution to logarithmically transformed data for absolute counts of CD4 and CD8 cells was superior to the fitting of an ellipse to untransformed data. Further analysis for another 147 subjects showed that the 95% tolerance prediction for the CD4/CD8 ratio in health could be stated with 95% confidence as 0.6 to 5.0. This approach allows clear definition of reference ranges for T cell tests in health and would also be applicable to results for patients with a disease such as HIV 1 infection in which a reference range for "well" patients exists and a change in the T cell ratio is of prognostic significance.