Pediatric Lead Toxicity Workup

Updated: Jun 22, 2016
  • Author: Mohamed K Badawy, MD, FAAP; Chief Editor: Timothy E Corden, MD  more...
  • Print
Workup

Approach Considerations

In the early 1990s, both the Centers for Disease Control and Prevention (CDC) and the American Academy of Pediatrics (AAP) recommended universal screening for lead toxicity in children at 1 and 2 years of age. With the subsequent decline in median blood lead concentrations, those organizations currently recommend performing environmental assessments to identify children at risk for lead exposure before screening. [8, 12]

Perform a rapid bedside glucose determination in children who present with altered mental status. Obtain serum pH and electrolyte levels, including calcium, magnesium, and phosphorus. Check for anion gap acidosis (see the Anion Gap calculator) that may be present in co-ingestions. A complete blood count (CBC) may reveal hypochromic microcytic anemia. Basophilic stippling of the erythrocytes, which is characteristic of lead poisoning, is uncommon in children.

Perform urinalysis. Children may appear mildly dehydrated, with concentrated urine and poor appetite. This can signal the beginning of the development of inappropriate secretion of antidiuretic hormone.

Whole blood lead level

Whole blood lead level (BLL) is the criterion standard for confirming the diagnosis of lead poisoning. For convenience, a fingerstick capillary lead level has been used for screening. Properly collected capillary samples have a 10% false-positive rate. Once an elevated lead level is detected, a venous lead level is assessed for confirmation.

Until recently, a BLL of 10 μg/dL or higher was considered to denote poisoning. Currently, the CDC recommends 5 μg/dL as a threshold for identifying children who have been exposed to lead and prompting measures to reduce the child’s future exposure to lead. That level corresponds to the 97.5th percentile of BLLs in US children aged 1–5 years from two consecutive cycles of the National Health and Nutrition Examination Survey (NHANES), which will be recalculated every 4 years. A BLL of 45 μg/dL remains the threshold for consideration of chelation therapy. [8]

Erythrocyte protoporphyrin

Erythrocyte protoporphyrin (EP) may be obtained in selected patients. Lead toxicity affects heme synthesis at several steps; this includes interference with the enzyme ferrochelatase, leading to the accumulation of EP. EP is easily detected because it fluoresces easily. EP is an adjunct for the diagnosis in the presence of elevated lead levels of 55 mcg and higher. At lead levels below that, EP is not a very sensitive measure, and its positivity declines. Therefore, EP is not used as a primary screening tool.

Hair samples

In Russia, hair sample is the standard for lead poisoning screening. However, studies have demonstrated that blood lead specimens are more sensitive than hair samples in detecting lead exposure.

Next:

Imaging Studies

Abdominal radiography

Presence of radiopaque flakes is a clear indicator of pica.

Long-bone radiography

Radiodensity may be detected at the distal metaphyseal area. These indications, known as lead lines, are true growth arrest lines and, although not pathognomonic, are associated with chronic lead exposure.

Chest radiography

This study is indicated in patients with lead encephalopathy to confirm the position of the endotracheal tube. Although radiographic findings of suspected aspirations may be initially absent, an initial radiograph is often helpful.

CT scanning

Head computed tomography (CT) scanning may be needed in patients who present with altered mental status to exclude cerebral edema and structural lesions.

Previous