Laboratory Studies
- Specific laboratory testing for metals should be undertaken when the likelihood of toxicity is significant, based on a history and/or symptoms consistent with excessive exposure. Please see the relevant articles for more detailed recommendations regarding the most reliable testing measures for individual metal toxicity (see Toxicity, Lead; Toxicity, Mercury; Toxicity, Arsenic; Toxicity, Iron).
- Where specific testing is indicated, samples should be sent in metal free containers.
- Hair analysis is not generally reliable and rarely indicated.
- Patients should be instructed to abstain from seafood and seaweed products prior to testing for metals like arsenic and mercury since elevated concentrations in patients who have not done so for at least several days to 1-2 weeks may simply reflect nontoxic organic forms ingested in the diet. Samples with elevated concentrations may also be sent for speciation for either of these metals to determine the relative contributions of organic forms versus inorganic forms.
- Some standard laboratory determinations may help make the diagnosis of heavy metal toxicity or help gauge its severity:
- Complete blood cell count (CBC) with peripheral smear
- Findings may include basophilic stippling of the RBCs on peripheral blood smears. Basophilic stippling is not specific for lead toxicity and may be observed in arsenic toxicity, sideroblastic anemia, and thalassemia.
- The anemia of lead toxicity may be normocytic or microcytic.
- Renal function tests
- Urine analysis (look for proteinuria)
- Liver function studies
- Complete blood cell count (CBC) with peripheral smear
Imaging Studies
- Abdominal radiographs are indicated in acute ingestions. Radio-opacities demonstrable in the gastrointestinal tract should be cleared by whole-bowel irrigation prior to instituting chelation therapy. Large, retained gastric foreign bodies (eg, bullets, shotgun cartridges, fishing sinkers, curtain weights) may cause lead toxicity and should be removed endoscopically if they do not pass, if serum lead concentrations are concerning or increasing, or if the patient becomes symptomatic.
- Several reported cases of patients who have injected elemental mercury subcutaneously and developed mercury toxicity have been documented. Radiographs of the suspect areas showing large subcutaneous deposits of radio-opaque material were helpful in confirming the diagnosis and need for surgical intervention to limit the exposure.
Other Tests
- ECG abnormalities may provide diagnostic clues in metal toxicity.
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| Metal | Acute | Chronic | Toxic Concentration | Treatment |
| Arsenic | Nausea, vomiting, "rice-water" diarrhea, encephalopathy, MODS, LoQTS, painful neuropathy | Diabetes, hypopigmentation/ hyperkeratosis, cancer: lung, bladder, skin, encephalopathy | 24-h urine: ≥50 µg/L urine, or 100 µg/g creatinine | BAL (acute, symptomatic) Succimer DMPS (Europe) |
| Bismuth | Renal failure; acute tubular necrosis | Diffuse myoclonic encephalopathy | No clear reference standard | * |
| Cadmium | Pneumonitis (oxide fumes) | Proteinuria, lung cancer, osteomalacia | Proteinuria and/or ≥15 µg/ g creatinine | * |
| Chromium | GI hemorrhage, hemolysis, acute renal failure (Cr6+ ingestion) | Pulmonary fibrosis, lung cancer (inhalation) | No clear reference standard | NAC (experimental) |
| Cobalt | Beer drinker’s (dilated) cardiomyopathy | Pneumoconiosis (inhaled); goiter | Normal excretion: 0.1-1.2 µg/L (serum) 0.1-2.2 µg/L (urine) | NAC CaNa2 EDTA |
| Copper | Blue vomitus, GI irritation/ hemorrhage, hemolysis, MODS (ingested); MFF (inhaled) | vineyard sprayer’s lung (inhaled); Wilson disease (hepatic and basal ganglia degeneration) | Normal excretion: 25 µg/24 h (urine) | BAL D-Penicillamine Succimer |
| Iron | Vomiting, GI hemorrhage, cardiac depression, metabolic acidosis | Hepatic cirrhosis | Nontoxic: < 300 µg/dL Severe: >500 µg/dL | Deferoxamine |
| Lead | Nausea, vomiting, encephalopathy (headache, seizures, ataxia, obtundation) | Encephalopathy, anemia, abdominal pain, nephropathy, foot-drop/ wrist-drop | Pediatric: symptoms or [Pb] ≥45 µ/dL (blood); Adult: symptoms or [Pb] ≥70 µ/dL[1] | BAL CaNa2 EDTA Succimer |
| Manganese | MFF (inhaled) | Parkinson-like syndrome, respiratory, neuropsychiatric[2] | No clear reference standard | * |
| Mercury | Elemental (inhaled): fever, vomiting, diarrhea, ALI; Inorganic salts (ingestion): caustic gastroenteritis | Nausea, metallic taste, gingivo-stomatitis, tremor, neurasthenia, nephrotic syndrome; hypersensitivity (Pink disease) | Background exposure "normal" limits: 10 µg/L (whole blood); 20 µg/L (24-h urine) | BAL Succimer DMPS (Europe) |
| Nickel | Dermatitis; nickel carbonyl: myocarditis, ALI, encephalopathy | Occupational (inhaled): pulmonary fibrosis, reduced sperm count, nasopharyngeal tumors | Excessive exposure: ≥8 µg/L (blood) Severe poisoning: ≥500 µg/L (8-h urine) | * |
| Selenium | Caustic burns, pneumonitis, hypotension | Brittle hair and nails, red skin, paresthesia, hemiplegia | Mild toxicity: [Se] >1mg/L (serum); Serious: >2 mg/L | * |
| Silver | Very high doses: hemorrhage, bone marrow suppression, pulmonary edema, hepatorenal necrosis | Argyria: blue-grey discoloration of skin, nails, mucosae | Asymptomatic workers have mean [Ag] of 11 µg/L (serum) and 2.6 µg/L (spot urine) | Selenium, vitamin E (experimental) |
| Thallium | Early: Vomiting, diarrhea, painful neuropathy, coma, autonomic instability, MODS | Late findings: Alopecia, Mees lines, residual neurologic symptoms | Toxic: >3 µg/L (blood) | MDAC Prussian blue |
| Zinc[3] | MFF (oxide fumes); vomiting, diarrhea, abdominal pain (ingestion) | Copper deficiency: anemia, neurologic degeneration, osteoporosis | Normal range: 0.6-1.1 mg/L (plasma) 10-14 mg/L (red cells) | * |
| *No accepted chelation regimen; contact a medical toxicologist regarding treatment plan. MODS, multi-organ dysfunction syndrome; LoQTS, long QT syndrome; ALI, acute lung injury; ATN, acute tubular necrosis; ARF, acute renal failure; DMPS, 2,3-dimercapto-1-propane-sulfonic acid; CaNa2 EDTA, edetate calcium disodium; MDAC, multi-dose activated charcoal; NAC, N -acetylcysteine. | ||||
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