The IQC samples were stable at 4oC for 20 days (CVr 0.2 - 4.15, CVt 0.18 - 4.64), at 4oC for 90 days (CVr 0.19 - 4.51, CVt 0.17 - 4.72), at - 20oC for 20 days (CVr 0.15 - 2.96, CVt 0.14 - 3.14), and at - 20oC for 90 days (CVr 0.14 - 2.79, CVt 0.14 - 3.23).