Table 2.

Characteristics of the serum samples

	Cases (n = 68)	Controls (n = 68)	P-value
Serum sample storage duration* (years)
Mean (SD)	11.2 (1.1)	11.2 (1.1)	0.900§
Hours in refrigerator†
Median (IQR)	22 (21-23)	22 (20-23)	0.845#
Days at -86°C‡
Median (IQR)	8 (6-11)	7 (5-11)	0.429#

SD: standard deviation; IQR: inter-quartile range; * Until date of experiment; ^† Between collection and centrifugation; ^‡ Between centrifugation and storage at liquid nitrogen; ^§ Independent samples T test; ^# Mann-Whitney U test.