Diagnosis of Leukemia: The Critical role of Laboratory tests 

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What is Leukemia?

Often referred to as blood cancer, leukaemia is the excessive proliferation of abnormal white blood cells in the bone marrow. The abnormal cells spill over to the bloodstream and onto other organs.

In this post, we will explore the critical role laboratory investigations play in the diagnosis of leukemias

Leukaemia can occur at any age, however, they are more common in early childhood (acute leukaemias) and in people older than 50 years (chronic leukemias). 

Leukemia Diagnosis - Photomicrograph of bone marrow aspriate in acute myeolgenous leukemia
Photomicrograph of bone marrow aspirate in acute myelogenous leukemia

Leukemia is responsible for significant cancer disease and deaths in Kenya. Accurate and timely diagnosis is essential for the initiation of appropriate therapy. It’s particularly important in childhood leukaemias as a complete cure is achievable if treatment is started early

In this article, I present an overview of basic tests used in the evaluation of a patient with leukaemia. These tests typically encompass a combination of haematological, biochemical, anatomic pathology, and molecular tests.

1. Complete Blood Count (CBC): 

The CBC is one of the initial tests used in the diagnosis of leukemia or raises suspicion about the disease. This test measures the number of red blood cells, white blood cells, and platelets in the blood. An abnormal CBC can be an initial indicator of leukemia.

It’s important to note that not all cases of leukemia will have elevated counts of the various blood cells.

A comprehensive post on CBC can be found here.

2. Peripheral Blood Smear: 

A microscopic examination of a blood smear can reveal abnormal blood cell morphology, such as immature or abnormal white blood cells, which may suggest leukemia. 

3. Bone Marrow Aspiration and Biopsy: 

These procedures involve taking a sample of bone marrow from the hip bone to examine under a microscope for the presence of leukemia cells.

It’s one of the most integral tests for leukemia diagnosis. Examining the blood-forming cells allows the pathologist to diagnose the exact type of leukemia and also assess the effect of leukemia on the bone marrow.

4. Flow Cytometry: 

Flow cytometry is used to analyze the surface markers on white blood cells. It’s used as a test for diagnosis of leukemia, as well as in classification leukemia cells into specific subtypes as outlined below.

Leukemia TypeFlow Cytometry Profile
Acute Myeloid Leukemia (AML)AML is characterized by the expression of myeloid markers such as CD13, CD33, and CD117, and lack of lymphoid markers such as CD3, CD19, and CD20. AML cells may also express HLA-DR and CD34.
Acute Lymphoblastic Leukemia (ALL)ALL typically shows the expression of TdT (terminal deoxynucleotidyl transferase), CD10, CD19, CD20, and CD22 in B-cell lineage, and CD3, CD5, CD7, and TdT in T-cell lineage.
Chronic Myeloid Leukemia (CML)CML is characterized by the presence of the Philadelphia chromosome (BCR-ABL1 fusion gene). Flow cytometry may show increased expression of myeloid markers such as CD13, CD33, and CD117.
Chronic Lymphocytic Leukemia (CLL)CLL cells typically express CD5, CD19, CD20 (dim), CD23, and CD43. They are negative for FMC7 and CD10.
Hairy Cell Leukemia (HCL)HCL is characterized by the expression of CD11c, CD25, CD103, and CD123. HCL cells are typically negative for CD10, CD5, and CD23.

5. Cytogenetic Analysis: 

This test examines the chromosomes within leukemia cells for abnormalities, such as translocations or deletions, which can provide important diagnostic and prognostic information.

5. Molecular Tests

a)  Genetic Testing: 

Polymerase Chain Reaction (PCR) and other molecular techniques can detect specific genetic mutations, such as the Philadelphia chromosome in chronic myeloid leukemia (CML).

b) FISH (Fluorescence In Situ Hybridization):

FISH is a cytogenetic technique that can detect specific genetic abnormalities, often used to confirm chromosomal changes associated with certain types of leukemia. 

Below are some of the common cytogenetic abnormalities

Risk GroupCytogenetic Abnormality
Better Riskinv(16), t(16;16), t(8;21), t(15;17)
Intermediate RiskNormal cytogenetics, +8, t(9;11); other chromosomal abnormalities
Poor Risk-5, 5q-, -7, 7q-, 11q23 other than t(9;11), inv(3), t(3;3), t(6;9),

t(9;22), complex findings (≥3 clonal chromosomal abnormalities)

C) Next-Generation Sequencing (NGS): 

NGS can provide detailed genetic information about leukemia cells, helping to guide treatment decisions and monitor for minimal residual disease.

D) Immunohistochemistry  (IHC) and Immunocytochemistry:

This technique uses antibodies to identify specific proteins in tissue samples and can be useful in diagnosing some types of leukemia. This is particularly useful in the detection of infiltration of leukemic cells in other organs. Immunocytochemistry can be employed in the analysis of cerebrospinal fluid (CSF)

In cases of acute leukemia, a lumbar puncture may be performed to check for the presence of leukemia cells in the cerebrospinal fluid.

6. Blood Chemistry Tests for Diagnosis of Leukemia: 

These tests can evaluate organ function and identify any abnormalities that may be related to leukemia or its treatment. Some of the chemistry tests used in diagnosis and treatment monitoring for leukemia include:

  1. Complete Metabolic Panel (CMP): A CMP measures various substances in the blood, including glucose, electrolytes (sodium, potassium, calcium), and liver and kidney function markers (bilirubin, albumin, creatinine). Abnormalities in these markers can indicate organ dysfunction, which may be secondary to leukemia or its treatment.
  2. Liver Function Tests (LFTs): LFTs assess the health of the liver and may include tests such as alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase. Elevated liver enzymes can be associated with certain types of leukemia or chemotherapy-related side effects.
  3. Kidney Function Tests: These include blood urea nitrogen (BUN) and creatinine measurements. Abnormal results can indicate kidney problems, which may be related to leukemia or its treatment.
  4. Electrolyte Panel (UECs): This measures levels of essential minerals like sodium, potassium, and calcium in the blood. Imbalances can occur due to leukemia or as side effects of treatment.
  5. Coagulation Profile: This assesses the clotting ability of the blood and may include tests like prothrombin time (PT), activated partial thromboplastin time (aPTT), D-Dimers as well as platelet levels. Leukemia can affect blood clotting, leading to abnormal results.
  6. Serum Lactate Dehydrogenase (LDH): Elevated LDH levels can be associated with tissue damage, including that caused by leukemia. It can serve as a general marker of disease activity.
  7. C-reactive Protein (CRP): Elevated CRP levels indicate inflammation in the body. Inflammatory processes may be associated with leukemia or infections.
  8. Serum Uric Acid: Increased uric acid levels can result from the rapid breakdown of leukemia cells and are commonly seen in some types of leukemia, such as acute lymphoblastic leukemia (ALL).
  9. Immunoglobulin Levels: Measuring immunoglobulins (antibodies) can help assess immune function, which may be compromised in leukemia.

Bonus: Tumor Lysis Syndrome (TLS) Markers

In cases where there is a risk of TLS (a complication of leukemia treatment), tests may be performed to monitor levels of potassium, phosphate, calcium, and uric acid to prevent and manage TLS.

Other Diagnostic Modalities 

Bone Scan and Imaging: Imaging studies like X-rays, CT scans, or MRI may be performed to assess bone involvement or detect enlarged lymph nodes and other organ involvement.

Bonus: Molecular Minimal Residual Disease (MRD) Assessment:

This test is used during and after treatment to detect small amounts of residual leukemia cells that may not be visible under the microscope.

We have to the end of our post on leukemia.  Below find a list of featured tests from this post. Remember, if you need consultation on the appropriate tests or interpretation of your tests, reach out to us.

Tests Related to leukemia Diagnosis

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