Zinc (Zn) challenge Test (1.5 hours)

Indications:

There are c.200 mammalian enzymes that require zinc as a co-factor and hence its deficiency has a multiplicity of effects in humans.
Only 1% of the total body zinc is in the plasma and there is poor exchange with other body tissues: plasma zinc is therefore not a good
index of total body status. Muscle zinc is the definitive measurement and leucoyte zinc correlates well with muscle zinc. In deficiency sweat zinc is a more reliable parameter than serum zinc, since the body removes zinc from the sweat to prevent its further loss. In children with zinc deficiency sweat zinc can be nearly zero.

Take a fasting blood sample. Blue top (trace- element free).

Give 220mg of Zn So4. 7 H2O in 75 ml of water (equivalent to 50 mg of zinc). Dilution of the zinc is required so that it does not act as an irritant to the stomach.

Take a second blood sample 90 minutes later and measure the serum zinc concentration in both samples.

The serum zinc in the 90 minute sample should be approximately 3 x the fasting zinc value; if not , this is evidence of zinc malabsorption.

Patient Instructions:

Patient should fast for at least 8 hours.

Sample Requirements:

2 x Navy Blue (EDTA) - Fasting and 90 minutes

Postal Samples Acceptable:

Yes