FIG. 3.

Source of absolute CD4 T-cell count bias in individual laboratories. The absolute CD4 T-cell count generated in each laboratory by the predicate or tetraONE method was subtracted from the five-laboratory median value by that method to determine whether method biases occurred in individual laboratories. A through E are laboratory designations. The shaded region indicates the interquartile range (25th and 75th percentiles) of these differences.