Identification of a Hemolysis Threshold That Increases Plasma and Serum Zinc Concentration

Killilea DW, Rohner F, Ghosh S, Otoo GE, Smith L, Siekmann JH, King JC

May 2017 – Journal of Nutrition

Plasma or serum zinc concentration (PZC or SZC) is the primary measure of zinc status, but it is not established how much hemolysis can occur without changing PZC/SZC concentrations. To estimate the effect of hemolysis on PZC/SZC concentrations, this study calculated a hemolysis threshold and then compared it with results from an in vitro study and a population survey. This study found a 5% increase in PZC/SZC was calculated to result from the lysis of 1.15% of the erythrocytes in whole blood, corresponding to ~1 g hemoglobin/L added into the plasma or serum. Similarly, the addition of simulated hemolysate to control plasma in vitro caused a 5% increase in PZC when hemoglobin concentrations reached 1.1860.10 g/L. In addition, serum samples from a population nutritional survey were scored for hemolysis and analyzed for changes in SZC; samples with hemolysis in the range of 1–2.5 g hemoglobin/L showed an estimated increase in SZC of 6% compared with non-hemolyzed samples. Each approach indicated that a 5% increase in PZC/SZC occurs at ~1 g hemoglobin/L in plasma or serum. This concentration of hemoglobin can be readily identified directly by chemical hemoglobin assays or indirectly by direct spectrophotometry or matching to a color scale. A threshold of 1 g hemoglobin/L is recommended for PZC/SZC measurements to avoid increases in zinc caused by hemolysis. The use of this threshold may improve zinc assessment for monitoring zinc status and nutritional interventions.