Figure 1Box plot showing the effect of repeated freezing and thawing on plasma concentrations of analytes. Lines on the box plot represent the median, 1st, and 3rd quartiles. Vertical lines represent the 10th and 90th centiles. IFN = interferon; IL = interleukin; MMP = matrix metalloproteinase; TNF = tumor necrosis factor; VEGF = vascular endothelial growth factor.
Figure 2Box plot showing the effect of repeated freezing and thawing on serum concentrations of analytes. Lines on the box plot represent the median, 1st, and 3rd quartiles. Vertical lines represent the 10th and 90th centiles. IFN = interferon; IL = interleukin; MMP = matrix metalloproteinase; TNF = tumor necrosis factor; VEGF = vascular endothelial growth factor.
Table 1Concentration changes of analytes induced by repeated freezing and thawing of plasma samples.
Analyte (pg/mL) |
Freeze–thaw cycles
|
p
|
2 cycles (baseline) |
3 cycles∗
|
4 cycles∗
|
5 cycles∗
|
IFN-γ |
6.14 ± 8.80 |
6.07 ± 7.74 |
5.49 ± 5.17 |
5.45 ± 6.05 |
0.205 |
|
(–1.2) |
(–10.6) |
(–11.3) |
|
IL-8 |
96.35 ± 164.46 |
96.82 ± 164.79 |
93.96 ± 154.99 |
94.58 ± 159.41 |
0.548 |
|
(+0.5) |
(–2.5) |
(–1.8) |
|
IL-15 |
1.70 ± 1.05 |
1.72 ± 1.00 |
1.69 ± 1.11 |
1.67 ± 1.26 |
0.963 |
|
(+1.0) |
(–0.7) |
(–1.7) |
|
IL-17A |
1.24 ± 1.59 |
1.20 ± 1.54 |
1.13 ± 1.36 |
1.084 ± 1.21 |
0.495 |
|
(–3.7) |
(–9.4) |
(–13.1) |
|
MMP7 |
2.34 ± 1.91 |
2.57 ± 2.11†
|
2.64 ± 2.18†
|
2.71 ± 2.03†
|
<0.001 |
|
(+9.9) |
(+12.5) |
(+15.6) |
|
TNF-α |
48.55 ± 49.42 |
47.48 ± 47.41 |
47.56 ± 47.69 |
47.02 ± 47.56†
|
0.072 |
|
(–2.2) |
(–2.0) |
(–3.2) |
|
VEGF |
134.39 ± 80.64†
|
144.40 ± 90.81†
|
148.67 ± 97.15†
|
154.69 ± 104.38†
|
0.124 |
|
(+7.4) |
(+10.6) |
(+15.1) |
|
VEGFR2 |
7,292.03 ± 878.64 |
7,259.46 ± 833.46 |
7,266.65 ± 866.95 |
7,278.96 ± 850.16 |
0.903 |
|
(–0.4) |
(–0.3) |
(–0.2) |
|
Table 2Concentration changes of analytes induced by repeated freezing and thawing of serum samples.
Analyte (pg/mL) |
Freeze–thaw cycles
|
p
|
2 cycles (baseline) |
3 cycles∗
|
4 cycles∗
|
5 cycles∗
|
IFN-γ |
8.11 ± 12.98 |
8.66 ± 14.13 |
8.82 ± 14.71 |
8.36 ± 13.76 |
0.327 |
|
(+6.8) |
(+8.8) |
(+3.2) |
|
IL-8 |
35.54 ± 71.31 |
36.25 ± 71.46 |
36.40 ± 71.28 |
34.22 ± 67.01 |
0.208 |
|
(+2.0) |
(+2.4) |
(–3.7) |
|
IL-15 |
1.54 ± 0.74 |
1.67 ± 0.73†
|
1.73 ± 0.71†
|
1.46 ± 0.66 |
0.001 |
|
(+8.7) |
(+12.4) |
(–4.7) |
|
IL-17A |
3.07 ± 3.45 |
3.59 ± 4.06†
|
3.29 ± 3.61 |
3.02 ± 3.39 |
0.110 |
|
(+17.2) |
(+7.4) |
(–1.6) |
|
MMP7 |
2.48 ± 1.50 |
2.59 ± 1.57†
|
2.65 ± 1.43†
|
2.64 ± 1.41†
|
0.004 |
|
(+4.1) |
(+6.9) |
(+6.5) |
|
TNF-α |
8.74 ± 5.09 |
9.04 ± 5.63†
|
9.17 ± 5.80†
|
8.82 ± 5.57 |
0.126 |
|
(+3.4) |
(+4.9) |
(+0.9) |
|
VEGF |
195.13 ± 99.52 |
197.53 ± 97.88 |
197.21 ± 97.99 |
208.84 ± 108.75†
|
0.107 |
|
(+1.2) |
(+1.1) |
(+7.0) |
|
VEGFR2 |
9,230.32 ± 1,877.97 |
9,264.60 ± 1,874.35 |
9,237.86 ± 1,806.16 |
9,267.74 ± 1,845.64 |
0.877 |
|
(+0.4) |
(+0.1) |
(+0.4) |
|