TABLE 6.

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

Phenotype	No. of samples	Median difference (1st quartile; 3rd quartile)b	P valuea
CD4	17	0.0 (−1.0; 2.0)	0.99
CD8	17	1.0 (0.0; 1.0)	0.14

^aWilcoxon 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⁺.

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