Various biomarkers remain intact in delayed sample processing

1. 72-hour delayed serum sample processing had no effect on testing for cytokines, chemokines, cfDNA, or coagulation in healthy volunteers and ICU patients 

Evidence Rating Level: 2 (Good) 

Plasma and serum markers are routinely collected for critically ill patients. Community hospitals, which care for the majority of Canadian patients, do not have the infrastructure to process and store these samples. A central site for processing has been suggested to allow community hospitals to conduct studies faster. However, the effect of delayed sample processing on serum markers, blood clotting factors, and other tests is unclear. This study aimed to determine the effect of delayed blood processing of up to 72 hours on the stability of plasma biomarkers commonly studied in critically ill patients. Participants had blood drawn into three citrate tubes and one EDTA tube. Aliquoted blood was kept at various re-processing conditions: RT vs 4˚C, and 0-, 24-, 48-, or 72-hours pre-processing delay. Delayed processing did not significantly affect levels of IL-6, IL-10, TNF, or IFN-γ (ANOVA, p = 0.31, p = 0.08, p = 0.30, p = 0.32, respectively). No significant changes in IL-6 levels were observed in citrate or EDTA samples from healthy volunteers (ANOVA p = 0.67 at RT and p = 0.35 at 4˚C) (S1 Fig) or ICU patients (ANOVA p = 0.55 at RT and p = 0.63 at 4˚C). Similarly, temperature did not affect IL-6 levels. No changes were seen in the tested chemokines either: IL-8, IP-10, MCP-1, MCP-4, MIP-1α, or MIP-1β (ANOVA, p = 0.31, p = 0.21, p = 0.36, p = 0.06, p = 0.57, and p = 0.35, respectively). To test cell death, cfDNA was examined. No changes were found after delayed processing in either temperature for both ICU and healthy participants (ANOVA p = 0.89 and p = 0.46, respectively). Finally, no changes were seen in coagulation studies including lag time and total thrombin formation. Therefore, delayed sample processing is a viable solution for conducting biosampling in community hospitals. 

Click to read the study in PLOSONE

Image: PD

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