CST3 and acute kidney injury: The results showed a significant difference in the levels of cystatin C between AKI and non-AKI children when their serum were stored at the temperatures of -70 °C (SMD = 1.06; 95% CI: 0.66-1.46; p < 0.001) and -80 °C (SMD = 0.97; 95% CI: 0.57-1.41; p < 0.001) but such association was not observed in patients whose sera were stored at -20 °C (SMD = 0.82; 95% CI: -0.19-1.83; p = 0.11).