Effect of delayed centrifugation of whole blood on serum samples stability

Background This study was aimed to investigate the effect of delayed centrifugation of whole blood samples on the quality of serum test results for five conventional clinical chemistry parameters and haemolysis index (HI). Methods Five aliquots of whole blood were prepared from each of 22 volunteer subjects. Aliquot 1 was immediately centrifuged and tested, aliquots 2–5 were centrifuged and tested after 3 h, 6 h, 12 h and 24 h of storage of whole blood at room temperature. Results variations of aspartate aminotransferase (AST), lactate dehydrogenase (LDH), potassium (K), total calcium (Ca), inorganic phosporous (iPhos) and haemolysis index (HI) were then compared with values of the baseline aliquot. Results After 3 h of storage all parameters except HI and AST exhibited modest but analytically significant variations. After 6 h of storage analytically significant variations were observed for AST, LDH, Ca and iPhos, whereas analytically significant variations were found for LDH, Ca and HI after 12 h of storage. All differences were analytically significant after 24 h of storage of whole blood at room temperature. Values exceeding the acceptable limits were observed for LDH, K and iPhos after 3 h of storage, for AST after 24 h of storage. Calcium remained stable throughout the study period. The HI displayed a considerable increase (i.e., 31.5%) after 24 h of storage. Conclusions The results of our experimental study about the impact of delayed centrifugation of whole blood specimens for obtaining serum attest that <3 h at room temperature should be considered the most appropriate time for storing samples before serum analysis.