Stability study of 17 clinical immunoassays analytes in serum and plasma samples within an automated storage and retrieval module: Assessment of add-on testing policies

• Most clinical immunoassays stored in a sample retrieval module remained stable for up to 72 h in both serum and plasma. • The evaporation process resulting from sample sealing is avoided. • Workflows are improved and laboratory resources are optimized resulting in greater sample stability. Additional tests are often requested on previously collected and stored samples. Automated storage and retrieval modules (SRMs) which are integrated into total laboratory automation (TLA) systems provide sealed, temperature-controlled storage and could potentially extend the scope of add-on testing. However, there is a lack of data regarding the stability of immunoassays when using an automated SRM. We evaluated the short-term stability of 17 immunoassay analytes. Fresh serum and plasma samples were analysed using the Atellica IM (Siemens Healthineers) system at baseline and after storage in the SRM at 2–8 °C for 24, 48, and 72 h. Stability was assessed as the mean percentage change compared to the total limit of change (TLC), derived from analytical and biological variability. Most analytes remained stable for up to 72 h in both matrices. No significant differences were observed between serum and plasma, except for free T4, which exceeded its TLC in plasma after 72 h (+9.2%). This study demonstrates that most clinical immunoassays assessed on the Atellica IM module remained stable for up to 72 h in serum and plasma when stored in an automated SRM environment, except for free T4, which remained stable for up to 48 h in plasma. These findings support the feasibility and safety of performing delayed add-on tests in laboratories using TLA.