Relationships between Plasma Zinc Concentrations and Clinical Signs of Zinc Deficiency

Abstract

Objectives: To evaluate the relationship between plasma zinc concentrations (PZC) and clinical signs of zinc deficiency, and to determine a cut-off for PZC below which individuals would have an increased likelihood of having clinical signs associated with zinc deficiency. Methods: Electronic bibliographic searches were performed to identify literature from experimental zinc depletion studies and case reports of individuals with acrodermatitis enteropathica (AE). Data extracted from relevant literature included demographic characteristics, PZC and the presence or absence of clinical signs likely associated with zinc deficiency. Results: PZC were significantly lower among experimentally depleted individuals with clinical signs than those who remained asymptomatic (zinc depletion studies: (36.0+16.8 vs. 67.9+13.3µg/dL, P<0.034) and among patients with clinical signs of AE before undergoing high-dose therapeutic zinc supplementation (35.0 (24.1, 47.4) µg/dL) compared with post-treatment values (108.0 (79.3, 127.0) µg/dL; P<0.01). Among individuals with restricted dietary Zn intake, PZC predicted clinical signs with 88% sensitivity and 75% specificity when using a cutoff of 60µg/dL, and 71% and 92% when applying a cutoff of 40µg/dL. Among individuals with AE, PZC predicted clinical signs with 88% sensitivity and 88% specificity when using a cutoff of 60µg/dL, and 63% and 95% when applying a cutoff of 40µg/dL. Conclusions: These analyses demonstrate a clear relationship between PZC and the presence of clinical signs associated with zinc deficiency among presumably healthy individuals undergoing periods of dietary zinc restriction, as well as individuals with AE pre- and post-treatment, further validating the utility of PZC as a biomarker of severe Zn deficiency.