Fig. 2. Difference plots and Passing–Bablok regression of storage and stability experiments. The data displayed in panels A, B, and C are results from the T₁ analyses for each plasma sample and are expressed as a percentage change in concentration from the baseline, T₀, on the Y-axis. The X-axis represents weeks in storage before the T₁ analysis. (A) Storage of non-stabilized plasma. Mean percentage concentration difference of +1.2% (median+0.5%). (B) Storage of PCA/DTPA-stabilized plasma. Mean percentage concentration difference of –0.2% (median+1.5%). (C) Comparison of PCA/DTPA-stabilized plasma with paired non-stabilized plasma. Numbers of samples per time point analyzed: 2 weeks (N=4), 7 weeks (N=7), 15 weeks (N=14), and 26 weeks (N=14). Mean percentage concentration difference of +9.9% (median+3.6%). (D) Passing–Bablok regression of non-stabilized plasma against PCA/DTPA-stabilized plasma. Concentrations determined through all experiments ranged from 2–812 μmol/L. The dashed lines in panels A, B, and C represent the ±25% APS for results ≥36.0 μmol/L. Abbreviations: PCA, perchloric acid; DTPA, diethylenetriaminepentaacetic acid; APS, allowable performance specifications; CI, confidence interval.

Ann Lab Med 2021;41:414~418 https://doi.org/10.3343/alm.2021.41.4.414