Iron Toxicity Workup

Updated: Feb 04, 2019
  • Author: Clifford S Spanierman, MD; Chief Editor: Michael A Miller, MD  more...
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Workup

Laboratory Studies

The workup for iron toxicity includes the following studies:

  • Serum iron

  • Glucose

  • Complete blood count (CBC)

  • Serum lactate

  • Arterial blood gas (ABG) - To assess for metabolic acidosis

  • Serum electrolytes - For anion gap calculation

  • Renal function tests

  • Liver function tests (LFTs)

  • Coagulation studies

  • Lipase and amylase levels - Occasional patients experience pancreatic injury

  • Pregnancy test in women of childbearing age

  • Blood type and cross-matching

  • Ferritin levels - Helpful for diagnosing chronic toxicity; levels may exceed 1000 mcg/L

For serum iron measurement, samples should be drawn at least 4 hours postingestion, to allow levels to reach steady state; however, levels drawn more than 6 hours after ingestion may underestimate toxicity because of ferritin binding and redistribution of iron. The significance of results is as follows:

  • In adults, levels may not correlate well with the clinical presentation

  • Mild-to-moderate toxicity generally manifests at levels of 350-500 mcg/dL

  • Persistently symptomatic patients with serum iron levels higher than 350 mcg/dL should be admitted

  • Hepatotoxicity usually is observed at levels higher than 500 mcg/dL

  • Levels higher than 800 mcg/dL are associated with severe toxicity

  • Patients with serum iron levels higher than 1000 mcg/dL should be in a facility that can provide age-appropriate intensive care

Glucose levels exceeding 150 mg/dL are common with severe iron toxicity. Following glucose levels is important because hepatic dysfunction may cause hypoglycemia.

On the CBC, a white blood cell (WBC) count of more than 15,000/mm3 is associated with severe iron poisoning. A CBC is also helpful because anemia from blood loss may develop.

LFTs are indicated because hepatic dysfunction is common in severe iron poisoning. The liver is the first organ outside of the GI tract to receive a large iron load, which enters through the portal blood supply.

Electrolyte measurements and renal function tests assist in calculation of the anion gap (see the Anion Gap calculator) and detection of electrolyte abnormalities and the presence of prerenal azotemia. Iron toxicity is one of the causes of acidosis with an increased anion gap, as noted in the mnemonic MUDPILES (M-methanol; U-uremia; D-diabetic ketoacidosis, alcoholic ketoacidosis; P-paraldehyde, phenformin; I-iron, isoniazid; L-lactic [ie, carbon monoxide, cyanide]; E-ethylene glycol; S-salicylates).

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Imaging Studies

Iron tablets remain radiopaque for a few hours postingestion, and may be visible on a kidneys, ureters, bladder (KUB) film. However, the absence of radiopacities does not rule out a significant or even potentially lethal ingestion. 

In dialysis patients, who routinely receive parenteral iron conjunction with erythropoiesis-stimulating agents for treatment of anemia, recent evidence suggests that measurement of liver iron content with magnetic resonance imaging (MRI) may be a valuable surrogate marker for total body iron. However, while these findings challenge the current reliance on transferrin saturation and serum ferritin levels as markers of iron load, the clinical relevance of MRI for this patient population remains to be determined. [15]

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