Zinc
There is no reliable method of assessing zinc stores. Suspected zinc deficiency
can best be tested by monitoring the symptomatic response to the administration
of zinc.
Plasma Zinc
A change in plasma zinc does not occur until zinc intake is extremely low. Only
10 to 20% of the zinc in blood is contained in the plasma. Most is bound to
alpha2-macroglobulins or to albumin. Hypoproteinemia or hyperproteinemia
can alter plasma zinc levels. Other factors that influence plasma zinc are
stress, infection, and hormones. Plasma zinc is useful for assessment only if
the effect of poor zinc status can be differentiated from these conditions.
Zinc Tolerance Test
This test measures the change in plasma zinc after zinc is orally administered.
A normal response is a doubling of plasma zinc peaking at three hours, though
the test is quite variable among subjects.
Hair Zinc
Hair zinc levels of less than 70 mcg per gram (gm) have been associated with
clinical signs of marginal zinc deficiency, such as impaired growth and poor
appetite, in children. Hair zinc measurements cannot be used in severe
malnutrition because of a decrease in the rate of hair growth in malnourished
patients.
Taste Acuity Tests
Decreased taste acuity is a symptom of zinc deficiency in both children and
adults. In a taste acuity test, solutions of varying concentrations of the four
different taste qualities (salt, sweet, bitter, and sour) are used. The test is
based on the detection and recognition thresholds for each taste quality.
