Comparison of enumerations of CD4+ or CD8+ T cells in cryopreserved PBMC stored at −70°C versus PBMC stored in liquid nitrogen before shipment on dry ice

PhenotypeNo. of samplesMedian difference (1st quartile; 3rd quartile)bP valuea
CD4170.0 (−1.0; 2.0)0.99
CD8171.0 (0.0; 1.0)0.14
  • a Wilcoxon matched-pair signed-rank test. Applied to the sample size of 17, this test had ≥80% power to detect a 3% difference in the percentage of either CD4+ or CD8+.

  • b Median differences are between the percentages of CD4+ or CD8+ in PBMC stored at −70°C and in PBMC in liquid nitrogen.