Soluble urokinase plasminogen activator receptor measurements:: Influence of sample handling

Aim: The influence of sample handling on soluble urokinase plasminogen activator receptor (suPAR) concentrations in serum and EDTA plasma was studied in 16 healthy premenopausal women. Method: Blood was collected in dry tubes and tubes containing EDTA and kept at 4degreesC or 20degreesC for 1, 3, 8, 24 or 72 hours before processing into serum or EDTA plasma. In addition, serum and EDTA plasma were frozen and thawed 1-8 times. All suPAR measurements were performed by ELISA. Results: No significant differences were found between serum or EDTA plasma suPAR concentrations when whole blood samples were kept for 1, 3, 8 or 24 hours. Significantly higher suPAR levels were found in samples kept for 72 hours at 20degreesC compared to samples processed into serum or EDTA plasma after short-term storage for no more than 24 hours after collection. No significant differences were observed when whole blood was kept at 4degreesC for up to 72 hours. Repeated freezing and thawing had no significant effect on the serum and EDTA plasma suPAR levels. Conclusion: suPAR values in blood samples are dependent on the handling procedures of the samples. All samples of whole blood must be processed into EDTA plasma or serum within 24 hours if kept at 20degreesC and within 72 hours if kept at 4degreesC. However, repeated freezing/thawing cycles had no influence on suPAR values in the samples.