At a Glance
Lead poisoning can cause anemia. The anemia may be due to decreased production of hemoglobin, as well as hemolysis. Signs of hemolysis may include scleral icterus and jaundice. Other symptoms associated with lead poisoning are covered in the chapter on laboratory testing for lead.
What Tests Should I Request to Confirm My Clinical Dx? In addition, what follow-up tests might be useful?
If a hemolytic anemia is in the differential, haptoglobin, lactate dehydrogenase (LDH), and bilirubin can be useful. Haptoglobin scavenges free hemoglobin and is low in hemolytic anemia.
Hemolysis may also lead to elevated LDH and bilirubin. LDH is present in red cells, and hemolysis causes release into the plasma. Bilirubin is a breakdown product of hemoglobin and becomes elevated as hemoglobin is released. Indirect hyperbilirubinemia is typically seen in hemolysis.
Review of the peripheral smear is crucial. Patients with lead poisoning will often show basophilic stippling. Microcytosis and hypochromia may be present, and reticulocyte counts may be elevated.
The direct antiglobulin test (DAT, direct Coombs test) should be negative (see chapter on laboratory testing for lead).
Are There Any Factors That Might Affect the Lab Results? In particular, does your patient take any medications – OTC drugs or Herbals – that might affect the lab results?
Haptoglobin is very sensitive but not specific for clinically significant hemolysis, as even small amounts of free hemoglobin can deplete normal levels of serum haptoglobin. It may also be decreased in liver disease. As haptoglobin is an acute phase reactant, it may be elevated in a number of diseases leading to difficulties in interpretation.
LDH is present in all tissues, including red cells, so elevations are consistent with hemolysis but very nonspecific, as any cellular damage may affect levels. As such, there are many other disorders that may cause an elevated LDH.
Other disorders may be associated with basophilic stippling.
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