Results from CD4 T cell count measurements in 182 HIV-1-infected adults and 76 HIV-1-infected children older than 5 years, expressed in absolute number (cells/μl) and in percentage carried out in parallel by the Auto40 flow cytometer and by the FACSCalibur. A, A’, C and C’. Passing-Bablok agreement tests between the CD4 T cell count results obtained by Auto40 and FACSCalibur flow cytometers, in absolute number (A and A’) and in percentage (C and C’). The diagonal dotted line represents the ideal line (no bias). The full line represents the regression line of the distribution; B, B’, D and D’. Bland-Altman analyses on the relative differences between the CD4 T cell counts obtained by Auto40 and FACSCalibur flow cytometers compared with the average CD4 T cell count, in absolute number (B and B’) and in percentage (D and D’). The full line represents the mean relative difference, and the dotted lines represent the superior and inferior limits of agreement. The arrow corresponds to the x abscise axis.