Reproducibility of LPA results for cryopreserved PBMC after variable periods of storage in liquid nitrogen. Reproducibility of LPA results for cryopreserved PBMC after variable periods of storage in liquid nitrogen. The data were derived from the laboratory with typical performance. Multiple aliquots from a single donor were tested after 1 to 15 months of storage in liquid nitrogen. The line represents the log SI regression as a function of time. Adriana Weinberg et al. Clin. Vaccine Immunol. 2009; doi:10.1128/CVI.00342-08