Pre-analytical stability of haematinics, lactate dehydrogenase and phosphate in whole blood at room temperature up to 24 h, and refrigerated serum stability of lactate dehydrogenase, folate and vitamin B12 up to 72 h using the CRESS checklist.

Objectives: There is a lack of analyte stability data in whole blood (WB). The aim of this study was to determine the allowable delay in WB processing for lactate dehydrogenase (LDH), folate, vitamin B12, iron and phosphate measurement. The stability of LDH, folate and vitamin B12 was also assessed in stored serum at clinically relevant time points.

Methods: Blood was taken from n=10 volunteers into Sarstedt serum gel tubes. We assessed stability in WB at room temperature up to 24 h, and stability in refrigerated serum up to 72 h. Mean percentage deviation at each time point was compared to criteria for minimum allowable bias.

Results: Results produced from one individual were removed due to discordant results, leaving n=9 specimens at each time point. Stability of folate and phosphate was variable in WB across 24 h, but was deemed to be clinically acceptable. LDH was unstable in WB, iron was stable for at least 12 h, and vitamin B12 and ferritin were acceptable for up to 24 h. Serum LDH, folate and vitamin B12 all demonstrated acceptable stability in refrigerated serum stored for up to 72 h.

Conclusions: Blood should ideally be centrifuged within 7 h for phosphate, LDH and folate, and 12 h for iron. However, for phosphate, folate and iron, there is likely to be little clinical impact if serum separation is delayed up to 24 h. Further research is needed to assess LDH stability in WB at 0-12 h, but changes are minimal at 12 h. All other analytes assessed showed acceptable stability across the time-points tested.