Effects of storage at-20°C on ischaemia-modified albumin results

Background Ischaemia-modified albumin (IMA) is being studied as a new marker for reversible ischaemia in patients presenting with possible cardiac chest pain. The conditions under which samples are stored prior to analysis may be critical in influencing the analytical result and hence the cut-off used in any particular study. Methods Sixty-eight samples taken during a study assessing the performance of IMA for risk stratification in patients presenting with possible cardiac chest pain were analysed both within 2.5 h of collection and after periods of storage at -20 degrees C. Results Samples stored at -20 degrees C yielded IMA values on average 3 units higher than those analysed within 2.5h (mean 90.5 vs. 87.5; P < 0.00001). A Bland-Altman plot showed that the difference was not concentration dependent. Conclusions These results indicate that decision cut-offs will be influenced by conditions of sample storage prior to IMA analysis, and that these should be stated in detail for each study.