Leukemia is a cancer of the blood and bone marrow characterized by an abnormal increase of immature white blood cells. Diagnosing and monitoring leukemia involves testing various blood cells counts and levels which may be elevated or decreased compared to normal.
Leukemia develops when the DNA of a blood cell is damaged, leading to uncontrolled growth and proliferation of abnormal white blood cells. This crowds out normal blood cell production in the bone marrow, leading to issues with infection, anemia, and bleeding. There are four main types of leukemia – acute myeloid leukemia (AML), acute lymphoblastic leukemia (ALL), chronic myeloid leukemia (CML) and chronic lymphocytic leukemia (CLL).
Testing blood cell counts and levels is crucial for diagnosing and monitoring leukemia. A complete blood count (CBC) provides an overview of all the cells in the blood and can detect abnormally high or low cell counts. More specific tests look at individual cell types and abnormalities to help classify the type of leukemia. Some key blood levels that can be affected by leukemia include:
White Blood Cells
– Total white blood cell (WBC) count
– Immature white cells such as blasts or promyelocytes
– Neutrophils, lymphocytes and monocytes
Red Blood Cells
– Red blood cell (RBC) count
– Hemoglobin
– Hematocrit
Platelets
– Platelet count
Understanding what blood levels may be abnormal can help diagnose leukemia earlier and monitor treatment response. This article will outline key blood markers affected in different leukemia types.
Acute Myeloid Leukemia
Acute myeloid leukemia (AML) is caused by a rapid growth of abnormal, immature myeloid white blood cells that build up in the bone marrow and blood. This disrupts normal blood cell production, leading to anemia and low platelet counts.
Some key characteristics and abnormal levels in AML include:
High White Blood Cell Count
The total WBC is often elevated in AML, sometimes exceeding 100,000/μL. This is due to an accumulation of abnormal, immature myeloblasts and promyelocytes. A normal WBC range is 4,500-11,000/μL.
Presence of Blast Cells
Myeloblasts are immature white blood cell precursors. Blasts make up <5% of cells in normal bone marrow but are significantly elevated in AML, usually >20%. Finding ≥20% blasts in the blood or bone marrow confirms an AML diagnosis.
Low Red Cell and Platelet Levels
The overcrowding of myeloid blast cells suppresses normal red blood cell and platelet production. This leads to:
- Anemia – Low RBC count, hemoglobin and hematocrit
- Thrombocytopenia – Platelet count <100 x 109/L
Neutrophil Levels
The neutrophil count may be low, normal or elevated in AML. A type called acute promyelocytic leukemia (APL) often presents with a high level of abnormal promyelocytes and low neutrophil count.
Acute Lymphoblastic Leukemia
Acute lymphoblastic leukemia (ALL) is caused by a rapid growth of immature lymphoid white blood cells called lymphoblasts. Abnormal lymphoblasts accumulate in the bone marrow and blood, displacing normal cells.
Key characteristics and abnormal levels seen in ALL are:
High White Blood Cell Count
Like AML, the total WBC count is often significantly elevated in ALL, sometimes exceeding 100,000/μL. This reflects the high number of abnormal lymphoblasts.
Presence of Blasts
Lymphoblasts exceed 20% of all cells in the bone marrow. This is a key diagnostic criterion for ALL. The lymphoblast percentage in blood is usually lower.
Low Neutrophil Count
ALL often presents with a reduced neutrophil count (neutropenia). This makes patients more susceptible to infections.
Normal or High Lymphocyte Count
The abnormal lymphoblasts may elevate the absolute lymphocyte count. However, normal lymphocytes are decreased.
Anemia and Thrombocytopenia
As with AML, the proliferation of leukemic lymphoblasts suppresses normal blood cell production leading to:
- Anemia – Low RBCs, hemoglobin and hematocrit
- Thrombocytopenia – Low platelet count
Chronic Myeloid Leukemia
Chronic myeloid leukemia (CML) causes increased production of abnormal granulocytes and bone marrow stem cells. It has a more indolent course compared to acute leukemias.
Characteristic findings include:
Elevated Total WBC Count
The total WBC is consistently elevated, often >100,000/μL, due to high numbers of neutrophils and immature myeloid cells.
Left Shifted Myeloid Cells
There are increased immature granulocytes such as metamyelocytes and myelocytes, described as a left shift. Blasts are usually <10%.
High Neutrophil Count
The neutrophil count is markedly elevated, typically >50,000/μL. Later stages may progress to a depletion of mature neutrophils.
Basophilia
There is an abnormally high basophil count, >200/μL. Basophils are a type of granulocyte.
Anemia and Thrombocytosis
CML causes:
- Anemia – Due to crowding out of RBC production
- Thrombocytosis – Elevated platelet count >600,000/μL
Chronic Lymphocytic Leukemia
Chronic lymphocytic leukemia (CLL) is characterized by a progressive accumulation of abnormal lymphocytes called lymphocyte-predominant small mature B cells.
Typical CLL blood count abnormalities include:
High Lymphocyte Count
There is an elevated absolute lymphocyte count, usually >5000/μL. This reflects the abnormal population of monoclonal B cells.
Low Neutrophil or Platelet Count
CLL may present with neutropenia or thrombocytopenia. However, this occurs later in advanced stages.
Normocytic Anemia
Anemia with a normal mean corpuscular volume (MCV) often develops in CLL due to the suppression of normal hematopoiesis.
Hypogammaglobulinemia
Many patients have a low immunoglobulin level due to impaired immune function and monoclonal B cell expansion.
Monitoring Treatment Response
Once leukemia is diagnosed, regular blood monitoring helps evaluate treatment response and detect relapse:
Complete Blood Count
The CBC monitors RBC, WBC and platelet counts. Treatment aims to return these to normal ranges.
Peripheral Blood Smear
Examines blood cell morphology for blast cells or abnormal cells suggesting refractory or relapsed disease.
Bone Marrow Biopsy
Analysis of bone marrow cell morphology, genetics and blast percentages to assess remission status.
| Test | Potential Findings in Leukemia |
|---|---|
| Complete blood count |
|
| Peripheral blood smear |
|
| Bone marrow biopsy |
|
Monitoring blood tests like the CBC detect early recurrence of leukemia before clinical relapse when treatment may have the best chance of controlling disease again.
Conclusion
Leukemia leads to disruption of normal hematopoiesis and blood cell production. Diagnosis and monitoring revolves around testing complete blood counts plus individual cell lines and bone marrow. Key markers that can indicate leukemia include elevated or decreased WBCs, abnormal or immature cells, changes in RBC and platelet levels, and high blast percentages in bone marrow. Familiarity with typical blood abnormalities assists prompt diagnosis and monitoring of treatment response in leukemia patients. Regular testing aims to achieve and maintain remission status.