Zinc is an essential trace mineral, meaning that the body needs it in small amounts but cannot produce it on its own. It plays a pivotal role in numerous biological processes, acting as a cofactor for over 300 enzymes involved in various functions such as metabolism, immune function, DNA synthesis, and wound healing. Additionally, zinc is vital for proper growth and development, making it especially critical during periods of rapid growth such as infancy, childhood, and adolescence. Zinc is essential for the synthesis and action of insulin.
Zinc testing
Typically involves measuring the concentration of zinc in the blood, plasma, serum, or hair. Each method offers unique insights into zinc status:
- Plasma or Serum Zinc Testing: Plasma or serum zinc levels are also commonly measured to assess zinc status.These tests may offer more stable results than blood zinc testing since plasma and serum zinc levels are less affected by short-term fluctuations.
- Urine zinc: When urine zinc levels are low alongside decreased serum zinc levels, it often suggests a confirmation of zinc deficiency. 24hours urinary zinc testing is preferred. No preservative should be added to collection container of urine.
- Hair Zinc Testing: Hair zinc testing involves analyzing the zinc content of hair samples. Since hair accumulates minerals over time, hair zinc levels can provide insights into long-term zinc status. However, factors such as hair color, texture, and environmental exposure may influence results.
Methodology
Inductively-coupled plasma/mass spectrometry (ICP/MS)
Indications of plasma Zinc testing
Zinc testing may be warranted in the following scenarios:
- Suspected Deficiency: Individuals experiencing symptoms suggestive of zinc deficiency, such as poor wound healing, impaired immune function, growth and development issues, hair loss, or skin problems, may benefit from zinc testing to assess their nutritional status.
- High-Risk Groups: Certain populations are at increased risk of zinc deficiency, including Alcohol abusers, pregnant and breastfeeding women, infants, children, adolescents, elderly individuals, vegetarians or vegans ( high phytates intake), individuals with malabsorption and those with chronic illnesses. patients taking total parenteral nutrition face also face zinc deficiency
- Monitoring Treatment: Zinc testing can be used to monitor the effectiveness of zinc supplementation in correcting deficiency and optimizing zinc status over time. follow oral zinc therapy in Wilson’s disease; confirm acrodermatitis enteropathica and follow therapy.
- Growth Retardation: Zinc plays a critical role in growth and development, making monitoring essential in cases of growth retardation, particularly in pediatric populations. Children with zinc deficiency may experience stunted growth and delayed sexual maturation. Regular monitoring of zinc levels enables healthcare providers to identify deficiencies early and implement interventions to support healthy growth and development.
| Patient Preparation | Patients should be advised to abstain from dietary supplements, vitamins, minerals, and nonessential over-the-counter medications for one week before sample collection, following their physician’s guidance. This step minimizes potential interference from these substances in the test results. |
|---|---|
| Collection tubes | Royal blue (No Additive), Royal blue (K2EDTA), or Royal blue (NaHep). |
| Specimen Preparation | Separate from cells ASAP or within 2 hours of collection Transfer 2 mL serum or plasma to anTrace Element-Free Transport Tube. |
| Storage/Transport Temperature | Room temperature. Also acceptable: Refrigerated or frozen. |
| Unacceptable Conditions | Samples must be separated from red cells or clots within two hours of collection to prevent inaccuracies. Collection in containers other than those specified, as well as transportation in non-designated containers, is unacceptable. Hemolyzed specimens are not suitable for testing RBC contain 10 times more zinc than serum) which can lead to erroneous results. |
Interpretation of zinc testing
- Normal Range: Typically, laboratories provide reference ranges for zinc levels in different sample types. Results within the reference range usually indicate adequate zinc status.
- Low Zinc Levels: Zinc levels below the reference range may suggest zinc deficiency. Clinical correlation with symptoms and medical history is essential for accurate interpretation.
- High Zinc Levels: Elevated zinc levels may indicate excessive zinc intake, supplementation, or underlying medical conditions such as zinc toxicity. Further evaluation may be necessary to determine the cause.
References:
Henry JB. Clinical Diagnosis and Management by Laboratory Methods.
Ruz M, Cavan KR, Bettger WJ, et al. Development of a dietary model for the study of mild zinc deficiency in humans and evaluation of some biochemical and functional indices of zinc status. Am J Clin Nutr. 1991; 53(5):1295-1303. PubMed 2021137
. Baselt RC, Cravey RH. Disposition of Toxic Drugs and Chemicals in Man. 4th ed. Foster City, Calif: Chemical Toxicology Institute;1995.