BCR-ABL Fusion Detection by FISH at Chughtai Lab

BCR-ABL Fusion Detection by FISH at Chughtai Lab

The BCR-ABL Fusion Detection by FISH at Chughtai Lab is a highly specialized molecular cytogenetic test designed to identify the presence of the BCR-ABL1 fusion gene. This abnormal gene is the hallmark of the Philadelphia chromosome, which results from a reciprocal translocation between chromosome 9 and chromosome 22, designated as t(9;22)(q34.1;q11.2). This genetic aberration plays a central role in the pathogenesis of certain hematological malignancies, most notably Chronic Myeloid Leukemia (CML) and a subset of Acute Lymphoblastic Leukemia (ALL). By utilizing Fluorescence In Situ Hybridization (FISH) technology, pathologists can visualize specific genomic sequences within individual cells, offering unparalleled precision in diagnosing, classifying, and monitoring these complex blood disorders.

Fluorescence In Situ Hybridization works by exposing denatured cellular DNA to fluorescently labeled single-stranded DNA probes that are complementary to the BCR and ABL1 gene sequences. When these probes hybridize with their target genomic regions, they emit distinct fluorescent signals under a specialized fluorescence microscope. In a normal cell, the BCR and ABL1 genes remain on their respective chromosomes, appearing as separate signals. However, in cells harboring the t(9;22) translocation, the fusion of these two genes brings the fluorescent probes into close proximity, creating a distinct fusion signal. This advanced technology allows for the analysis of both interphase and metaphase cells, providing a rapid and highly sensitive alternative to traditional karyotyping, which requires actively dividing cells and has lower resolution.

Evaluating the BCR-ABL1 fusion gene is of paramount clinical importance in modern hematooncology. The diagnostic value of this test extends beyond simple identification; it helps clinicians stratify risk, predict prognosis, and formulate targeted therapeutic strategies. The discovery of Tyrosine Kinase Inhibitors (TKIs), such as imatinib, nilotinib, and dasatinib, has revolutionized the treatment of BCR-ABL1-positive leukemias. Because these therapies specifically target the constitutively active tyrosine kinase protein produced by the BCR-ABL1 fusion gene, confirming the presence of this genetic marker is an absolute prerequisite for initiating TKI therapy. Consequently, the BCR-ABL Fusion Detection by FISH at Chughtai Lab serves as an indispensable tool for guiding personalized treatment and ensuring optimal patient outcomes across Pakistan.

Clinical Procedure: What to Expect

Patient Preparation

Proper preparation is essential to ensure specimen integrity and accurate diagnostic results. Patients undergoing the BCR-ABL Fusion Detection by FISH at Chughtai Lab should observe the following guidelines:

• No Fasting Required: There is generally no requirement to fast before this test. Patients can consume food and liquids normally unless instructed otherwise by their physician.
• Medical History Documentation: Patients must provide a complete clinical history, including any current diagnoses of leukemia, previous genetic test results, and details of ongoing treatments, particularly Tyrosine Kinase Inhibitor (TKI) therapy.
• Medication Review: Inform the healthcare provider of all current medications, including over-the-counter drugs, blood thinners, and supplements. Do not discontinue any prescribed medication unless explicitly directed by the managing physician.
• Consent and Documentation: A signed informed consent form is typically required for genetic and molecular testing. Ensure all laboratory requisition forms are filled out completely by the referring oncologist or hematologist.
• Specimen Specifics: If the test is to be performed on a bone marrow aspirate, the patient will receive specific instructions regarding the procedure, which is performed by a hematologist or trained clinical specialist in a controlled clinical setting.

During the Procedure

The procedure for BCR-ABL Fusion Detection by FISH depends on whether the sample is peripheral blood or bone marrow aspirate. The laboratory process at Chughtai Lab follows strict quality control protocols:

• Sample Collection (Peripheral Blood): A phlebotomist will locate a suitable vein, typically in the inner elbow, cleanse the area with an antiseptic, and insert a sterile needle to draw blood into a green-top (sodium heparin) tube. This process takes only a few minutes and involves minimal discomfort.
• Sample Collection (Bone Marrow Aspirate): If bone marrow is required, a hematologist performs an aspiration, usually from the posterior iliac crest (hip bone). The area is numbed with a local anesthetic, and a specialized needle is used to extract a small amount of liquid bone marrow. Patients may feel a brief, deep ache during aspiration.
• Laboratory Processing: Once the sample reaches the cytogenetics laboratory at Chughtai Lab, the cells are cultured (if necessary), harvested, and fixed onto microscope slides.
• Hybridization: The slides are treated to denature the DNA, and locus-specific fluorescent probes for BCR (typically labeled green) and ABL1 (typically labeled red/orange) are applied. The slides are incubated to allow the probes to hybridize with the target DNA.
• Fluorescence Microscopy: A molecular pathologist analyzes the slides using a high-resolution fluorescence microscope equipped with specialized filters. The pathologist counts a minimum of 200 interphase nuclei to determine the percentage of cells displaying the fusion signal (typically appearing as yellow or overlapping red-green signals).
• Safety and Comfort: All blood draws and bone marrow collections are performed using strict aseptic techniques to prevent infection. Patients undergoing bone marrow aspiration are monitored briefly post-procedure to ensure there is no active bleeding from the site.

When is a BCR-ABL Fusion Detection by FISH Performed?

Suspected Chronic Myeloid Leukemia (CML)

Physicians request this test immediately when a patient presents with clinical signs and laboratory findings suggestive of Chronic Myeloid Leukemia. CML is a clonal myeloproliferative neoplasm characterized by the overproduction of granulocytes. The presence of the BCR-ABL1 fusion gene is the defining diagnostic criterion for CML, found in more than 95% of cases. Identifying this fusion confirms the diagnosis and distinguishes CML from other myeloproliferative disorders or reactive leukocytosis.

Evaluation of Philadelphia Chromosome-Positive Acute Lymphoblastic Leukemia (Ph+ ALL)

In patients diagnosed with Acute Lymphoblastic Leukemia, determining the BCR-ABL1 status is critical for risk stratification and treatment planning. Approximately 20% to 30% of adult ALL cases and 3% to 5% of pediatric ALL cases are positive for the Philadelphia chromosome (Ph+ ALL). This subtype is historically associated with a poorer prognosis, but the integration of TKIs into chemotherapy regimens has significantly improved outcomes. The FISH test allows for rapid identification of this genetic marker at diagnosis.

Monitoring Tyrosine Kinase Inhibitor (TKI) Therapy Response

For patients undergoing treatment with TKIs, regular monitoring of the BCR-ABL1 clone is essential to assess therapeutic efficacy. While quantitative PCR (qPCR) is the gold standard for monitoring deep molecular response, FISH is highly valuable for assessing cytogenetic response, particularly in the early stages of therapy or when evaluating compliance and potential resistance. A declining percentage of BCR-ABL1 positive cells indicates a favorable response to treatment.

Investigating Unexplained Leukocytosis and Splenomegaly

When a patient presents with persistent, unexplained elevation of the white blood cell count (leukocytosis), often accompanied by an increase in immature myeloid precursors and an enlarged spleen (splenomegaly), clinicians must rule out underlying malignancies. The BCR-ABL FISH test provides a definitive answer, helping to differentiate reactive leukemoid reactions from clonal hematological malignancies that require immediate, specialized intervention.

Assessment of Minimal Residual Disease (MRD) and Relapse

Following bone marrow transplantation or intensive chemotherapy, patients are monitored closely for minimal residual disease (MRD) or early signs of disease recurrence. The BCR-ABL FISH test can detect low levels of the fusion gene in interphase cells, providing an early warning of impending relapse before clinical symptoms or abnormal blood counts manifest, allowing oncologists to adjust therapeutic strategies proactively.

What Does a BCR-ABL Fusion Detection by FISH Detect?

The BCR-ABL Fusion Detection by FISH is designed to identify specific cytogenetic configurations and cellular abnormalities. The test detects and quantifies the following clinical and genetic findings:

• Presence of the classic t(9;22)(q34;q11) reciprocal translocation.
• Absence of the BCR-ABL1 fusion gene, ruling out classic Philadelphia-positive leukemias.
• Percentage of interphase nuclei positive for the BCR-ABL1 fusion signal.
• Standard dual-color, dual-fusion signal patterns (two fusion signals, one free green, and one free red signal).
• Atypical or variant translocation patterns involving third or fourth chromosomes.
• Deletions of the derivative chromosome 9, which can have prognostic significance in certain clinical contexts.
• Presence of extra copies of the Philadelphia chromosome (double Ph+), indicating clonal evolution or disease progression.
• Amplification of the BCR-ABL1 fusion gene locus, which may correlate with resistance to TKI therapy.
• Normal diploid signal patterns (two separate green and two separate red signals) in healthy cells.
• Mosaicism, showing a mixture of normal and abnormal cell populations.
• Identification of BCR-ABL1 positive clones in lymphoid versus myeloid lineages when combined with immunophenotyping.
• Early cytogenetic response to therapeutic interventions.
• Persistence of the leukemic clone during clinical remission (minimal residual disease).
• Clonal expansion of abnormal cells over sequential testing intervals.
• Atypical signal configurations, such as single fusion signals or extra isolated signals, requiring further genomic characterization.
• Quality control parameters, including hybridization efficiency and background fluorescence levels.
• Correlation of cytogenetic findings with peripheral blood cell morphology.
• Presence of subclonal populations with varying genetic configurations.
• Genetic changes associated with the transition from the chronic phase to the accelerated or blast phase of CML.
• The baseline genetic profile prior to the initiation of targeted tyrosine kinase inhibitor therapy.

Turnaround Time and Report Access at Chughtai Lab

Chughtai Lab is committed to providing accurate and timely diagnostic results. Due to the complex nature of molecular cytogenetics, which involves cell harvesting, hybridization, and microscopic analysis by specialized pathologists, the turnaround time for the BCR-ABL Fusion Detection by FISH is typically within 5 to 7 working days. This timeframe ensures that every sample undergoes rigorous quality control and double-reporting by qualified cytogeneticists to eliminate any margin of error.

Patients and referring physicians can access reports conveniently through multiple digital channels. Once the report is finalized, an automated SMS notification is sent to the patient’s registered mobile number. Reports can be downloaded directly from the official Chughtai Lab website using the patient ID and case number. Additionally, the Chughtai Lab mobile application offers a seamless interface for viewing, downloading, and sharing diagnostic reports with healthcare providers, facilitating prompt clinical decision-making.

BCR-ABL Fusion Detection by FISH Findings Overview

Structure / Parameter Evaluated	Normal Findings	Possible Abnormal Findings
BCR-ABL1 Fusion Signal	Absent (0% of analyzed nuclei)	Present (variable percentage of positive nuclei)
Signal Pattern (Dual Color Probe)	2 Separate Green (BCR), 2 Separate Red (ABL1)	1 Green, 1 Red, 2 Fusion (Yellow/Overlapping) signals
Philadelphia Chromosome t(9;22)	Not detected	Detected in metaphase or interphase cells
Derivative Chromosome 9	Intact, normal structure	Deleted or rearranged (associated with altered prognosis)
Clonal Evolution Markers	None detected	Extra copies of Ph chromosome, trisomy 8, or isochromosome 17q
BCR-ABL1 Copy Number	Standard single copy per chromosome	Gene amplification or multiple fusion signals per cell
Interphase Nuclei Analysis	100% normal signal distribution	Varying percentages of abnormal nuclei (e.g., 5% to 98%)

Note: Diagnostic findings should always be interpreted by a qualified healthcare professional together with the patient’s symptoms, medical history, physical examination, laboratory investigations, previous imaging studies, and other relevant clinical information. Additional investigations or specialist consultation may be recommended depending on the findings.

Why Choose Chughtai Lab for BCR-ABL Fusion Detection by FISH?

• Experienced Healthcare Professionals: Chughtai Lab boasts a team of highly qualified pathologists, molecular biologists, and cytogeneticists specializing in hematooncology.
• Patient-Focused Care: The laboratory prioritizes patient comfort, safety, and clear communication throughout the testing process.
• Quality Diagnostic Services: Utilizing state-of-the-art molecular diagnostic equipment and standardized protocols ensures high diagnostic accuracy.
• Professional Reporting: Detailed and comprehensive reports provide clear cytogenetic interpretations to assist oncologists in treatment planning.
• Modern Diagnostic Approach: Implementation of advanced FISH probe technology allows for the detection of subtle and atypical genetic translocations.
• Comfortable Environment: Collection centers across Pakistan are designed to provide a welcoming, hygienic, and professional experience for patients.
• Convenient Location: With a vast network of diagnostic centers and home sample collection services, Chughtai Lab is easily accessible nationwide.
• Commitment to Accurate Diagnosis: Strict internal and external quality assurance programs guarantee reliable and reproducible results for critical oncological markers.