• The plasma or serum zinc (Zn) concentration is widely used to assess Zn status. It can be measured using several methods, including flame atomic absorption spectroscopy (FAAS), inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma atomic emission spectroscopy (ICP-AES), and colorimetry.
• Zn has multiple biochemical functions (e.g., there are more than 300 Zn-containing metallo enzymes). Therefore, the clinical presentation of Zn deficiency is highly variable. Signs and symptoms include depressed growth, increased incidence of infection, skin lesions, and alopecia. An autosomal recessive inborn error affecting Zn absorption is called acrodermatitisenteropathica.
• Although measured in both serum and plasma, Zn is usually measured in plasma because of possible Zn contamination from erythrocytes, platelets, and leukocytes induced by clotting and centrifugation. Zn can also be measured in urine and hair.
• The reference range for Zn in plasma is 80-120 μg/dL. Fasting morning samples lower than 70 μg/dL on several occasions require further investigation, whereas results lower than 30 μg/dL suggest deficiency.
• Zn serum concentrations are influenced by gender, age, use of steroid-based medications including oral contraceptives, time of blood collection, and fasting status. Zn levels decrease during acute phase reactions because of the redistribution of albumin (and, therefore, of protein-bound Zn) into interstitial spaces and an induction of hepatic metallothionein synthesis with subsequent sequestration of Zn. Therefore, Zn levels should be interpreted in conjunction with markers of an acute-phase reaction. Zn concentrations can also be elevated because of artifactual contamination from the blood collection tubes.
