Stability of 54 biochemical analytes in capped serum samples stored at 4–8 °C: a 72-h longitudinal evaluation

Abstract Objectives To evaluate the stability of 54 biochemical analytes in blood samples that were centrifuged, capped, and stored at 4–8 °C for 24, 48, and 72 h. Methods A prospective study was conducted with 588 serum samples using the Cobas ® 8000 modular analyzer and the Cobas ® p701 post-analytical unit (Roche Diagnostics). Analytes were measured at baseline and after 24, 48, and 72 h. Stability limits were determined by comparing percentage deviations against the maximum permissible instability criteria established. Results The majority of the evaluated analytes showed acceptable analytical stability for up to 72 h. However, seven analytes remained stable for only up to 48 h (albumin, alkaline phosphatase, calcium, free prostatic specific-antigen, gamma-glutamyl transferase, potassium and total protein). Ten analytes showed reduced stability, remaining reliable for only 24 h (chloride, folate, parathyroid hormone, triglycerides and vitamin B12) or less (alanine aminotransferase, alpha-amylase, inorganic phosphate, troponin and uric acid). Conclusions Refrigerated storage at 4–8 °C ensures the analytical stability of 38 out of 54 biochemical analytes for up to 72 h, validation that safely covers typical weekend operational delays and requests for add-on testing. Nonetheless, specific time restrictions must be strictly enforced for the unstable analytes identified to guarantee clinical accuracy.