Correlation of fresh-shipped and cryopreserved samples in all three assays. (A, C, E) Correlation graphs of fresh-shipped versus cryopreserved PBMC samples for tetramer, CFC, and ELISPOT, respectively. Correlation coefficients (r) are shown for all data as well as for CMV seropositive donors only. Open symbols represent CMV seronegative donors; closed symbols, seropositive donors (*, CMV serostatus unknown). The diagonal line represents the line of perfect agreement between the assays. (B, D, F) Within-donor differences are shown for fresh-shipped versus cryopreserved responses. Bars represent the median difference of all donors. All statistics are based on a natural logarithm transformation, which was done to better approximate a bivariate normal distribution.
Maecker et al. BMC Immunology 2005 6:17 doi:10.1186/1471-2172-6-17