Table 1.

Summary statistics for serum measurements of β-trace protein and β2 microglobulin before and after a single freeze–thaw cycle, N=172 pairs.

	β-Trace protein (mg/L)	β2 Microglobulin (mg/L)
Before freeze–thaw, reference rangea	0.40 to 1.36	1.50 to 4.56
After freeze–thaw, reference rangea	0.43 to 1.45	1.51 to 4.43
Before freeze–thaw, mean (SD)	0.75 (0.23)	2.42 (0.72)
After freeze–thaw, mean (SD)	0.70 (0.22)	2.42 (0.74)
Mean difference (before–after) (95% CI)	−0.05 (−0.06 to −0.04)	0.01 (−0.01 to 0.02)
P-valueb	0.006	0.35
CVDifference, (95% CI)c	13.2 (11.8 to 14.6)	3.85 (3.25 to 4.44)
Pearson’s correlation, r	0.94	0.99
Intra-class correlation coefficient (95% CI)	0.91 (0.86 to 0.97)	0.98 (0.98 to 0.99)
Deming regression coefficient, β1 (SE)	0.91 (0.03)	1.03 (0.01)
Deming regression constant, βo (SE)	0.02 (0.02)	−0.06 (0.03)
Linear regression with no constant, β (SE)	0.93 (0.01)	1.00 (0.003)

^aThe reference range represents the 2.5th to 97.5th percentiles.

^bPaired t-test of the hypothesis that the means are equal.

^cConfidence intervals generated from 1000 bootstrap replications.