Hemolytic Anemia Evaluation
Evaluation of hemolytic anemias of obscure cause
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Hemolytic anemia (HA) is characterized by increased red cell destruction and a decreased red cell life span. Patients have decreased hemoglobin concentration, hematocrit, and red blood cell count. Blood smear abnormalities may include spherocytes, acanthocytes, schistocytes, stomatocytes, polychromasia, and target cells. Osmotic fragility also is increased due to the presence of spherocytes.
HAs may be congenital or acquired. Inherited hemolytic disorders may include red cell membrane fragmentation, red cell enzyme defects, or abnormal structure of the hemoglobin molecule in the red cell. Examples of congenital HA include spherocytic HA and glucose-6-phosphate dehydrogenase (G-6-PD) deficiency, which may be intermittent, often brought on by certain drugs, fava bean ingestion, or infections. Some hemoglobinopathies also may demonstrate a hemolytic process. Examples of acquired HA include: autoimmune HA, direct Coombs-positive HA, disseminated intravascular coagulation, and drug-induced HA.
This consultative evaluation looks for the cause of increased red cell destruction and includes testing for hereditary spherocytosis, hemoglobinopathies, and red cell metabolism abnormalities.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
Definitive results and an interpretive report will be provided.
An interpretive report will be provided.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Preliminary screening tests, such as complete blood count with peripheral smear and direct Coombs test, should be run before ordering this evaluation.
This group of tests should not ordinarily be requested in patients who are likely to have immune hemolytic anemia (HA), such as that due to either warm or cold antibodies or to paroxysmal nocturnal hemoglobinurias. Coombs tests, tests for cold agglutinins, sucrose hemolysis, and Hams and Crosby tests are not part of the HA evaluation. In general, the foregoing tests should have been done prior to requesting a HA evaluation. Since Wilson disease is another rare cause for acute intermittent hemolysis, testing for Wilson disease also may be appropriate prior to requesting HA evaluation.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Beutler E: Glucose-6-phosphate dehydrogenase deficiency and other enzyme abnormalities. In Hematology. Fifth edition. Edited by E Beutler, MA Lichtman, BS Coller, TJ Kipps. New York, McGraw-Hill Book Company, 1995, pp 564-581
2. Hoyer JD, Hoffman DR: The thalassemia and hemoglobinopathy syndromes. In Clinical Laboratory Medicine. Second edition. Edited by KD McMlatchey. Philadelphia, Lippincott, Williams and Wilkins, 2002, pp 866-895