A Formula for Correcting Plasma Zinc Levels against Protein Concentration

Abstract

Plasma zinc and total protein concentrations were measured in 13 normal volunteers, before and after a five-minute occlusion of the antecubital vein with a sphygmomanometer cuff. The percentage increment before and after five minutes of venous occlusion was 10.2 ± 4.7% for total protein and 8.8 ± 6.0% for zinc concentration. Both these differences were statistically significant (p < 0.001). We propose an equation for correction of plasma zinc levels according to concentration of total proteins. Using this equation the corrected values of plasma zinc before and after 5 minutes of venous occlusion were similar, that is, 12.33 ± 1.94 and 12.20 ± 2.05 μmol/l. In addition we found that of seven hypoproteinemic patients on continuous ambulatory peritoneal dialysis (CAPD) who had low plasma zinc levels compared to normal (uncorrected for protein concentration) controls, only two had “true” hypozincemia when their plasma zinc was corrected against protein using this formula and compared to normals (corrected for protein) controls. The paper discusses the clinical usefulness of this adjustment of measurements of plasma zinc concentration.