Approach Considerations
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.
Except for rare circumstances, there is little or no value in measuring lead in urine or hair. Because of the pharmacokinetics of lead clearance, urine lead changes more rapidly and may vary independently of BLL. Urine lead is less validated than BLL as a biomarker of external exposure, or as a predictor of health effects. Lead in hair may be a reflection of external contamination rather than internal lead dose and laboratory analysis is not standardized. [9]
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.
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. [10]
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.
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.
