Fig. 6

Assay measurements remain stable in specimens exposed to up to 7 freeze-thaw cycles, 168 h at 4 °C, 24 h at room temperature, or 30 days at − 20 °C. a Samples from low-, intermediate-, and high-concentration plasma pools were assayed after a number a freeze-thaw cycles. Samples from b low-, c intermediate-, and d high-concentration plasma pools were also assayed after incubation at 4 °C, room temperature, or − 20 °C. (i) Normalized concentrations relative to samples directly stored at − 80 °C and (ii) variation in sample duplicates are plotted. Points represent (i) mean normalized concentration or (ii) CV of duplicates and (i) error bars represent ±SD. For some points, the error bars are shorter than the height of the symbol and therefore are not shown. The effect of plasma temperature modification on measured concentration was analyzed by repeated measures one-way ANOVA with Dunnett’s multiple comparisons test; no significant differences were found. CV: coefficient of variation, RT: room temperature