Inorganic Phosphorus and Potassium Are Putative Indicators of Delayed Separation of Whole Blood

The delayed separation of whole blood can influence the concentrations of circulating blood components, including metabolites and cytokines. The aim of this study was to determine whether clinical-biochemistry analytes can be used to assess the delayed separation of whole blood.

We investigated the plasma and serum concentrations of five clinical-biochemistry analytes and free hemoglobin when the centrifugation of whole blood stored at 4°C or room temperature was delayed for 4 hours, 6 hours, 24 hours, or 48 hours, and compared the values with those of matched samples that had been centrifuged within 2 hours after whole-blood collection.

The inorganic phosphorus (IP) levels in the plasma and serum samples were elevated ≥ 1.5-fold when whole-blood centrifugation was delayed at room temperature for 48 hours. Furthermore, the IP levels in the plasma samples showed excellent assessment accuracy [area under the receiver-operating-characteristic curve (AUC) > 0.9] after a 48-hour delay in whole-blood separation, and high sensitivity (100%) and specificity (95%) at an optimal cutoff point. The IP levels in the serum samples also exhibited good assessment accuracy (AUC > 0.8), and high sensitivity (81%) and specificity (100%). The potassium (K(+)) levels were elevated 1.4-fold in the serum samples following a 48-hour delay in whole-blood separation. The K(+) levels showed excellent assessment accuracy (AUC > 0.9) following a 48-hour delay in whole-blood separation, and high sensitivity (95%) and specificity (91%) at an optimal cutoff point.

Our study showed that the IP and K(+) levels in the plasma or serum samples could be considered as putative indicators to determine whether whole-blood separation had been delayed for extended periods.