Laboratory Codes for Heavy Metal Testing
For testing lead, arsenic, and mercury levels, use venous blood sampling for lead and mercury, and 24-hour urine collection or spot urine for arsenic, with testing performed by OSHA-designated laboratories using inductively coupled plasma-mass spectrometry (ICP-MS). 1, 2
Specimen Type and Collection Method
Lead Testing
- Venous blood is the gold standard for lead measurement, providing the most accurate assessment of current lead exposure and body burden 1, 3
- Whole blood lead measurement should be obtained from clinical laboratories designated by OSHA as meeting specific proficiency requirements 1
- Avoid capillary (fingerstick) samples for diagnostic purposes, as they are prone to contamination from lead on the skin surface and should only be used for initial screening 1, 4
- Any elevated capillary result must be confirmed with venous blood 1, 4
Mercury Testing
- Blood mercury reflects recent exposure to both organic (methylmercury) and inorganic mercury forms 2
- Whole blood is the preferred specimen for mercury biomonitoring 2
- Hair and nails primarily reflect organic mercury exposure except in populations with high inorganic mercury exposure 2
Arsenic Testing
- Urine is the preferred specimen for arsenic exposure assessment 2
- Total urinary arsenic may reflect both organic (from seafood) and inorganic arsenic, so arsenic speciation is needed in populations with dietary seafood consumption 2
- 24-hour urine collection or spot urine with creatinine adjustment can be used 1, 2
Laboratory Testing Method
- Inductively coupled plasma-mass spectrometry (ICP-MS) is the current standard analytical method for multi-element heavy metal analysis 2, 5
- Select laboratories that achieve routine performance within ±2 μg/dL for lead rather than the federally permitted ±4 μg/dL 1, 4
- For lead testing specifically, laboratories must meet OSHA proficiency requirements; OSHA maintains a list of designated laboratories 1
Comprehensive Heavy Metal Panel Approach
- Consider ordering a broad multi-element panel rather than single-element testing, as studies show 42-48% of specimens initially negative for one element had elevations in other toxic metals when expanded panels were used 5
- A comprehensive panel typically includes blood analysis for lead, cadmium, and mercury, plus urine analysis for arsenic, cadmium, copper, lead, mercury, and zinc 1, 5
- Hair and nail analysis for heavy metals (arsenic, lead, mercury) reflects past exposure rather than current levels 1, 2
Important Testing Considerations
For Lead Specifically
- Blood lead measurements integrate multiple exposure sources and routes 2
- Zinc protoporphyrin testing is not recommended for blood lead concentrations <25 μg/dL due to poor sensitivity 1
- Laboratory error at low blood lead levels can be ±2-4 μg/dL, so serial measurements help establish true trends 1, 4
For Arsenic Specifically
- Request arsenic speciation (inorganic arsenic metabolites: arsenite, arsenate, monomethylarsonic acid, dimethylarsinic acid) if dietary seafood consumption is significant, as arsenobetaine from seafood is non-toxic 2
- Baseline urine arsenic without speciation may lead to false positives in populations consuming seafood 2
For Mercury Specifically
- Blood mercury reflects recent exposure with a short half-life 2
- For chronic low-level exposure assessment, hair or toenail samples may provide better long-term exposure information 2
Clinical Context for Ordering
- In occupational settings, venous blood lead testing is required for workers exposed to airborne lead ≥30 μg/m³, though testing should be considered for all lead-exposed workers including those with ingestion exposure 1
- For children with suspected lead exposure, venous blood lead is required for confirmation of any elevated capillary screening result 1, 4
- When evaluating distal symmetric polyneuropathy, blood, urine, hair, and nail analysis for heavy metals (arsenic, lead, mercury, thallium) may be indicated based on clinical suspicion 1