Comparison of CD4 counts measured on ST (index test), at different time intervals, and EDTA at day 0 (reference test). A: box-and-whisker plots displaying the median and upper and lower quartiles. B and C: scatter plots displaying correlation. D and E: Bland-Altman plots showing the mean difference (solid line) and 95% lower limits of agreement (dotted lines). Blue vertical dashed lines indicate CD4 T cells thresholds of 350 cell/μL and 500 cells/μL.