Increasing albumin to creatinine ratio (ACR) within the normal range is a risk factor for cardiovascular disease in the general population. Clinical and epidemiological studies often store urine samples for long durations prior to ACR assessment. The stability of ACR at the lowest urinary albumin concentrations during prolonged storage has not been previously studied because routine clinical assays can't quantify very low concentrations of albumin.
Chapman D [et al]. Stability of urinary albumin and creatinine after 12 months storage at -20 °C and -80 °C. Practical Laboratory Medicine. 2019 Mar 22;15:e00120