Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (973 page)

   Lead: <10 μg/dL (blood); <5 μg/dL (blood) for children under 6 years

   Mercury: <10 ng/mL blood

   Selenium: 58–234 ng/mL blood

   Thallium: <10 ng/mL serum

   Zinc: 0.6–1.2 μg/mL plasma

   Use

   Many are naturally occurring in the environment (soil, air, water) and human body.

   Depending on the metal, heavy metals have widespread use in consumer products such as cooking utensils, cosmetics, pharmaceutical products, packing materials, insecticides, wood products, batteries, computer chips, semiconductor industry, military, barometers, gauges, wiring, paint, fungicides, preservatives, canning industry, glass, plastic, ceramics, smelting, and refining and construction industries.

   Limitations

   Typically, whole blood, free of clots, is tested. (Note exceptions above under normal range.)

   Specimen must be collected using a procedure that minimizes environmental contamination. Specimen container must be trace-element free (e.g., royal blue sodium EDTA tube).

HEMATOCRIT (Hct)
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   Definition and Use

   Hct is the ratio of spun RBCs to plasma, reflecting the volume of packed RBCs. It may be performed manually following centrifugation or calculated in automated counters as the product of MCV and the RBC count. It is expressed as a percentage.