Comparability of flow cytometric enumerations of CD4+ and CD8+ T cells in fresh and cryopreserved PBMC

PhenotypeNo. of subjects per labMedian (%) in fresh (frozen) PBMCMedian difference between % in fresh and % in frozen PBMC (range)aMedian correlation coefficient (range)bNo. (%) of labs with significant correlationsc
CD4+17-2626 (25)0.0 (−3.0-1.0)0.86 (0.46-0.94)6 (86)
CD8+17-2651 (48)1.0 (−2.5-3.3)0.82 (0.74-0.94)7 (100)
  • a Differences in the percentages of the indicated phenotype in fresh versus frozen PBMC were calculated by subtracting the percentage of the indicated phenotype in cryopreserved PBMC from the percentage of the phenotype in fresh PBMC. The data represent the median differences across all laboratories and the ranges of median differences at individual laboratories.

  • b Spearman correlation analysis of fresh and frozen PBMC in each laboratory was used to generate a coefficient of correlation. The data indicate the median and the range of medians of the coefficient of correlations at individual laboratories.

  • c Significance was defined by P ≤ 0.05.