When should testing for heavy metals be done?

When to Test for Heavy Metals

Heavy metal testing should be performed when there are specific clinical indications such as unexplained neurological symptoms, liver abnormalities of uncertain cause in individuals 3-45 years old, suspected occupational or environmental exposure, or symptoms associated with known metal toxicity. 1

Clinical Indications for Heavy Metal Testing

Neurological Presentations

• Unexplained neurological symptoms including headache, irritability, fatigue, and muscular pains
• Cognitive or psychomotor impairment
• Symptoms resembling Parkinson's disease (manganism)
• Peripheral neuropathy with unknown cause 2, 1

Hepatic and Gastrointestinal Presentations

• Liver abnormalities of uncertain cause in individuals 3-45 years old
• Unexplained cholestasis or liver failure
• Gastrointestinal neuropathies without identified cause 2, 1

Exposure-Based Indications

• Suspected occupational exposure (mining, manufacturing, battery production)
• Environmental exposure concerns (contaminated water, soil)
• Long-term parenteral nutrition (>30 days) especially with impaired liver function 2, 1

Specific Clinical Scenarios

• Iron deficiency with manganese exposure (increases risk of manganese toxicity)
• Patients on dialysis (aluminum toxicity risk)
• Children with developmental delays and environmental risk factors 2, 1

Testing Methods and Specimen Selection

Blood Testing

• Venous blood sampling is the preferred method for most heavy metals (lead, mercury, cadmium, arsenic)
• Must use lead-free collection devices to prevent contamination
• Samples should be collected before blood transfusion or IM administration of supplements 1

Urine Testing

• Complete 24-hour urine collection essential for copper, mercury, arsenic, and cadmium
• Urine must be collected in metal-free containers (especially important for copper testing)
• Store samples at 2-8°C for up to 7 days 2, 1, 3

Other Specimen Types

• Hair and nail analysis can provide information about long-term exposure but have limitations in clinical interpretation
• Liver biopsy is the gold standard for copper measurement in Wilson's disease (≥250 μg/g dry weight) 1

Monitoring Frequency

• For manganese toxicity monitoring: not more frequent than at 40-day intervals (biological half-life) 2
• For individuals receiving aluminum-containing medications: at least yearly monitoring 1
• For patients on long-term parenteral nutrition with manganese: regular monitoring, especially with intake >55 μg/day 2

Interpretation of Results

Critical Values Requiring Intervention

• Whole blood or serum manganese values greater than twice the upper limit of normal laboratory reference ranges 2
• Copper values >100 μg/24 hours (suggestive of Wilson's disease) 1
• Serum ceruloplasmin <200 mg/L or 20 mg/dL (suggests deficiency) 1

Cautions in Interpretation

• Laboratory error can be significant at low blood lead levels
• Capillary blood samples should be confirmed with venous samples for lead
• Interpreting 24-hour urinary copper excretion can be difficult due to overlap with findings in other liver diseases 1

Special Considerations

Contamination Prevention

• Use proper collection techniques to prevent sample contamination
• Avoid copper contamination in collection apparatus for copper testing
• Use lead-free collection devices for blood lead testing 1

Storage Requirements

• Blood samples should be stored at -20°C for up to 30 days or colder for longer storage
• Urine samples should be stored at 2-8°C for up to 7 days 1

Heavy metal testing should be approached systematically based on clinical presentation and exposure history. The choice of testing method should be guided by the specific metal of concern and the clinical context, with venous blood and 24-hour urine collection being the most reliable methods for most heavy metals.