Autoimmune hemolytic anemia laboratory findings
Jump to navigation
Jump to search
|
Autoimmune hemolytic anemia Microchapters |
|
Differentiating Autoimmune hemolytic anemia from other Diseases |
|---|
|
Diagnosis |
|
Treatment |
|
Case Studies |
|
Autoimmune hemolytic anemia laboratory findings On the Web |
|
American Roentgen Ray Society Images of Autoimmune hemolytic anemia laboratory findings |
|
Directions to Hospitals Treating Autoimmune hemolytic anemia |
|
Risk calculators and risk factors for Autoimmune hemolytic anemia laboratory findings |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-In-Chief: Prashanth Saddala M.B.B.S; Shyam Patel [2], Irfan Dotani [3]
Overview
Laboratory findings in patients with autoimmune hemolytic anemia include anemia, positive Coombs test, positive indirect antiglobulin test, hemoglobinuria, low haptoglobin, increased spherocytes, and elevated lactate dehydrogenase (LDH). Not all patients will have all of these findings. The severity of hemolysis will determine the degree of laboratory abnormalities.
Laboratory Findings
A variety of laboratory tests can be used to help diagnose autoimmune hemolytic anemia.
- Complete blood count:
- The complete blood count (CBC) will reveal decreased hemoglobin, typically less than 10 g/dl.
- By definition, autoimmune hemolytic anemia is characterized by anemia. In some cases, patients can also have a low platelet count (thrombocytopenia), such as in the case of Evan's syndrome, which is a syndrome of autoimmune hemolytic anemia plus immune thrombocytopenic purpura (ITP).
- The white blood cell count is normal in autoimmune hemolytic anemia, unless a patient is receiving treatment with corticosteroids, which can cause leukocytosis, or elevated white blood cell count.
- Coombs' test:
- This is also known as the direct antiglobulin test.
- The Coombs test assesses for the presence of antibodies attached to a patient's red blood cells, which is a key feature of autoimmune hemolytic anemia.
- The test is performed by collecting peripheral blood containing red blood cells, which presumably harbor antibodies on their surfaces, then adding in a Coombs reagent and assessing for agglutination. If agglutination occurs in the presence of the Coomb's reagent, this indicates the presence of antibodies on the surface of red blood cells.[1]
- Of note, the Coomb's test can be negative in 3-10% of patients.[2] The reasons for a negative Coombs' test include inability to detect a minimal amount of immunoglobulin G (IgG) on the red blood cell surface.[3] Another reason for a false-negative Coombs' test is the presence of immunoglobulin A (IgA) on the red blood cell surface, instead of IgG.
- Other laboratory tests that can be done in the setting of false-negative Coombs test include flow cytometry and antibody elution techniques.[2]
- Indirect antiglobulin test:
- This is also known as the indirect Coomb's test.
- The indirect antiglobulin test involves detection of circulating anti-red blood cell antibodies.
- The test involves using reagent red blood cell, which are commercially available, and adding the patient's serum (which presumably contains the anti-red blood cell antibodies). Then, the Coombs's reagent is added, and agglutination is observed.
- Hemoglobin in the urine:
- Elevated urine hemosiderin indicates intravascular hemolysis.
- Reticulocyte count:
- Patients with autoimmune hemolytic anemia will mount a compensatory response to red blood cell destruction by increasing erythroid production from the bone marrow.
- The immediate precursor to mature red blood cells is the reticulocyte.
- An elevated reticulocyte count is an indication of active hemolysis.
- Serum bilirubin:
- Bilirubin is a breakdown product of biliverdin, which is a breakdown product of heme, which is found in hemoglobin.
- Upon red blood cell destruction in autoimmune hemolytic anemia, free heme is released into the circulation and is eventually broken down to bilirubin.
- An elevated total bilirubin and indirect (unconjugated) bilirubin is an indication of hemolysis.
- Patients with autoimmune hemolytic anemia typically have total bilirubin level greater than 1 g/dl and indirect bilirubin of 50% or greater of the total bilirubin level.
- Serum haptoglobin:
- Bilirubin binds to haptoglobin, and therefore haptoglobin decreases in autoimmune hemolytic anemia.
- The level is typically less than 8 mg/dl in patients with active hemolytic anemia.
- Serum LDH:
- Lactate dehydrogenase (LDH) is an intracellular enzyme in red blood cells and is released upon destruction of red blood cells.
- Patients with autoimmune hemolytic anemia have elevated LDH (typically greater than 300 units per liter).
- However, this test has low specificity, as LDH can be elevated in other conditions such as tumor lysis syndrome or ventricular assist device thrombosis.
- Peripheral blood smear:
- The peripheral blood smear allows for direct visualization of the morphology of red blood cells.
- In autoimmune hemolytic anemia, red blood cells have a spherical shape and are known as spherocytes.
- This is in contrast to the normal shape of red blood cells, which is biconcave with a large surface area.
- The pathophysiology behind the formation of spherocytes is that splenic macrophages remove a portion of the red blood cell membrane, resulting in loss of the normal biconcave shape of erythrocytes.
- Complete blood count:
References
- ↑ Biswas S. Chandrashekhar P. Varghese M (2007). "Coomb's Positive Hemolytic Anemia Due To Insect Bite". Oman Med J. 22 (3): 62–3. PMC 3294156. PMID 22400097.
- ↑ 2.0 2.1 Berentsen S, Sundic T (2015). "Red blood cell destruction in autoimmune hemolytic anemia: role of complement and potential new targets for therapy". Biomed Res Int. 2015: 363278. doi:10.1155/2015/363278. PMC 4326213. PMID 25705656.
- ↑ Park SY, Kim S, Kim ES, Choi SU, Hyun HJ, Ahn JY; et al. (2012). "A Case of Non-Hodgkin's Lymphoma in Patient with Coombs' Negative Hemolytic Anemia and Idiopathic Thrombocytopenic Purpura". Cancer Res Treat. 44 (1): 69–72. doi:10.4143/crt.2012.44.1.69. PMC 3322204. PMID 22500164.