Flowcytometry for PNH Diagnostic Test at Chughtai Lab

Flowcytometry for Paroxysmal Nocturnal Hemoglobinuria (PNH) at Chughtai Lab

Paroxysmal Nocturnal Hemoglobinuria (PNH) is a rare, acquired, life-threatening hematologic disorder characterized by complement-mediated intravascular hemolysis, a high risk of venous and arterial thrombosis, and varying degrees of bone marrow failure. The underlying pathophysiology of PNH involves a somatic mutation in the phosphatidylinositol glycan class A (PIG-A) gene within hematopoietic stem cells. This mutation leads to a deficiency or complete absence of glycosylphosphatidylinositol (GPI) anchors, which are essential for securing specific regulatory proteins to the cell membrane. Most notably, the loss of GPI-anchored proteins CD55 (decay-accelerating factor) and CD59 (membrane inhibitor of reactive lysis) leaves red blood cells highly vulnerable to destruction by the body’s own complement system. Flow cytometry has emerged as the gold standard diagnostic method for PNH, offering unparalleled sensitivity and specificity compared to historical tests like the Ham test or sucrose hemolysis test. At Chughtai Lab, this specialized investigation is performed using state-of-the-art multi-color flow cytometers, providing clinicians with precise quantification of the PNH clone size across multiple cell lineages.

The clinical utility of flow cytometry in PNH diagnosis lies in its ability to detect and quantify the absence of GPI-anchored proteins on the surface of red blood cells (erythrocytes), granulocytes, and monocytes. Because red blood cells have a shortened lifespan in PNH due to active hemolysis, and because blood transfusions can temporarily introduce normal GPI-positive red blood cells, evaluating white blood cells (granulocytes and monocytes) is critical for accurate clone size determination. White blood cells do not undergo complement-mediated lysis in the same manner as red blood cells, making them a more stable and reliable indicator of the true PNH clone size. Chughtai Lab utilizes advanced gating strategies and high-sensitivity assays, including Fluorescently Labeled Aerolysin (FLAER), which directly binds to the GPI anchor itself, to ensure even the smallest PNH clones are detected with extreme precision.

Clinical Procedure: What to Expect

Patient Preparation

• No Fasting Required: Patients do not need to fast before the blood draw. Routine dietary intake is permitted.
• Clinical History: It is essential to provide a complete clinical history, including recent blood transfusions, as transfused red blood cells can dilute the PNH clone and lead to an underestimation of the PNH erythrocyte population.
• Medication Details: Inform the healthcare provider of all current medications, especially any complement inhibitors (such as eculizumab or ravulizumab) or immunosuppressive therapies.
• Hydration: Ensure adequate hydration prior to the procedure to facilitate easier venous access.

During the Procedure

The procedure for Flowcytometry for PNH at Chughtai Lab is straightforward and minimally invasive, following strict clinical guidelines to maintain sample integrity. A phlebotomist will identify a suitable vein, typically in the inner elbow, and cleanse the area with an antiseptic solution. A sterile needle is inserted to collect a peripheral blood sample into a vacuum tube containing ethylenediaminetetraacetic acid (EDTA) as the anticoagulant. The collection process takes only a few minutes and may cause a mild, temporary pinching sensation. Once collected, the sample is gently inverted to mix the anticoagulant and labeled with the patient’s unique identification details. The sample is then transported at room temperature to the specialized hematopathology laboratory, where it must be processed within established stability windows to ensure cell viability. In the laboratory, the sample is incubated with a panel of fluorochrome-conjugated monoclonal antibodies and FLAER, followed by analysis on a multi-color flow cytometer by experienced laboratory technologists.

When is a Flowcytometry for PNH Performed?

Unexplained Coombs-Negative Hemolytic Anemia

Physicians frequently request flow cytometry for PNH when a patient presents with signs of intravascular hemolysis—such as elevated lactate dehydrogenase (LDH), low haptoglobin, and hemoglobinuria (dark-colored urine)—but tests negative for autoimmune hemolytic anemia via the Direct Antiglobulin Test (DAT or Coombs test). PNH is a non-autoimmune hemolytic anemia, and identifying the absence of CD55 and CD59 on red blood cells confirms that the hemolysis is due to complement-mediated destruction rather than antibody-mediated targeting, guiding appropriate therapeutic interventions.

Unexplained Thrombosis at Atypical Sites

Thrombosis is the leading cause of mortality in PNH patients, often occurring in atypical anatomical locations such as the hepatic veins (Budd-Chiari syndrome), portal vein, mesenteric veins, splenic vein, renal veins, or cerebral venous sinuses. When a patient presents with unexplained thrombosis in these unusual sites, especially in the presence of mild cytopenias or signs of hemolysis, clinicians order PNH flow cytometry. Early detection is vital, as standard anticoagulation alone may be insufficient without addressing the underlying complement activation.

Evaluation of Bone Marrow Failure Syndromes

There is a close pathophysiological relationship between PNH, Aplastic Anemia (AA), and Myelodysplastic Syndromes (MDS). Small PNH clones are frequently detected in patients with these bone marrow failure syndromes, often representing an immune-escape mechanism where GPI-deficient stem cells survive autoimmune destruction. Flow cytometry is performed at diagnosis and during routine follow-up in AA and MDS patients to monitor for the emergence or expansion of a PNH clone, which can significantly alter the clinical management and prognosis.

Monitoring Known PNH Patients

For patients already diagnosed with PNH, serial flow cytometry testing is performed to monitor the clone size over time. This is particularly important for patients receiving targeted complement inhibitors, as monitoring the proportion of Type I, II, and III red blood cells helps assess treatment efficacy, detect breakthrough hemolysis, and monitor for clonal evolution. Changes in clone size can signal disease progression or response to therapy, allowing hematologists to make informed adjustments to the patient’s treatment plan.

Investigation of Unexplained Cytopenias

Persistent, unexplained cytopenias—such as refractory anemia, leukopenia, or thrombocytopenia—warrant investigation for underlying clonal disorders. When these cytopenias are accompanied by clinical symptoms like severe fatigue, abdominal pain, dysphagia, or erectile dysfunction (which result from nitric oxide depletion caused by free hemoglobin), flow cytometry for PNH is indicated to rule out or confirm a PNH clone as the contributing factor to the bone marrow insufficiency.

What Does a Flowcytometry for PNH Detect?

Flowcytometry for PNH is a highly sophisticated assay that evaluates multiple parameters across different blood cell lineages to provide a comprehensive diagnostic profile. The test specifically detects and quantifies:

• The percentage of Type I red blood cells (normal expression of CD55 and CD59).
• The percentage of Type II red blood cells (partial deficiency of CD55 and CD59).
• The percentage of Type III red blood cells (complete absence of CD55 and CD59, highly susceptible to lysis).
• FLAER (Fluorescently Labeled Aerolysin) binding on granulocytes to assess overall GPI anchor integrity.
• FLAER binding on monocytes to confirm myeloid lineage involvement.
• CD24 expression on granulocytes as a lineage-specific GPI-anchored marker.
• CD14 expression on monocytes as a lineage-specific GPI-anchored marker.
• CD157 expression on both granulocytes and monocytes for high-sensitivity PNH clone detection.
• The total PNH clone size within the granulocyte population, which reflects the true clonal hematopoiesis.
• The total PNH clone size within the monocyte population to correlate with granulocyte findings.
• The presence of minor PNH clones (often less than 1%) in patients with bone marrow failure.
• The presence of large PNH clones (typically greater than 50%) associated with classic hemolytic PNH.
• Discrepancies between red blood cell and white blood cell clone sizes, indicating active hemolysis or recent transfusions.
• The recovery of normal erythropoiesis following therapeutic interventions.
• The absence of non-specific antibody binding through strict gating protocols.
• The viability of analyzed cells to ensure accurate antigen quantification.
• The presence of dual populations of red blood cells in post-transfusion settings.
• The stability or expansion of the PNH clone over successive evaluations.
• The exclusion of inherited GPI-anchor deficiencies (such as congenital CD59 deficiency).
• The precise cellular composition of the peripheral blood sample analyzed.

Turnaround Time and Report Access at Chughtai Lab

At Chughtai Lab, we understand the clinical urgency associated with diagnosing complex hematological conditions like PNH. The Flowcytometry for PNH test is performed at our state-of-the-art central reference laboratory in Lahore, which is equipped with advanced multi-color flow cytometers and staffed by specialized hematopathologists. The turnaround time for this highly specialized investigation is typically 3 to 5 working days. This timeline ensures that the sample undergoes meticulous preparation, multi-parametric analysis, and expert interpretation. Once the report is finalized and signed off by a Consultant Hematopathologist, patients and referring physicians receive an automated SMS notification. Reports can be accessed instantly and downloaded online through the Chughtai Lab website or the dedicated Chughtai Lab mobile application. Physical copies of the report can also be collected from any of our convenient collection centers located across Pakistan.

Flowcytometry for PNH Findings Overview

Structure / Parameter Evaluated	Normal Findings	Possible Abnormal Findings
Granulocyte FLAER / CD24	Uniformly positive (high binding/expression)	Presence of a distinct population with deficient or absent FLAER/CD24 expression, indicating a PNH clone.
Monocyte FLAER / CD14	Uniformly positive (high binding/expression)	Presence of a distinct population with deficient or absent FLAER/CD14 expression, confirming myeloid involvement.
Red Blood Cell CD59	Uniformly positive (Type I cells)	Presence of Type II (partially deficient) or Type III (completely deficient) red blood cells.
Red Blood Cell CD55	Uniformly positive (normal expression)	Deficient or absent CD55 expression on a subset of red blood cells.
Granulocyte Clone Size	0% (No PNH clone detected)	Detected clone size ranging from minor (<1% in bone marrow failure) to large (>50% in classic PNH).
Monocyte Clone Size	0% (No PNH clone detected)	Detected clone size closely correlating with the granulocyte clone size.
Erythrocyte Clone Size	0% (No PNH clone detected)	Detected clone size, often significantly smaller than the WBC clone due to active hemolysis or transfusions.

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 Flowcytometry for PNH?

• Experienced Healthcare Professionals: Our hematopathology department is led by highly qualified Consultant Hematopathologists with extensive experience in diagnosing complex blood disorders.
• Patient-Focused Care: We prioritize patient comfort and convenience throughout the testing process, from sample collection to report delivery.
• Quality Diagnostic Services: Chughtai Lab adheres to stringent international quality standards, ensuring highly accurate and reproducible test results.
• Professional Reporting: Our reports provide detailed quantification of clone sizes across multiple lineages, aiding clinicians in precise therapeutic decision-making.
• Modern Diagnostic Approach: We utilize state-of-the-art multi-color flow cytometry technology and high-sensitivity FLAER assays for superior diagnostic accuracy.
• Comfortable Environment: Our numerous collection centers across Pakistan offer a clean, professional, and welcoming environment for all patients.
• Convenient Location: With a vast network of laboratories and collection points nationwide, accessing our diagnostic services is easy and convenient.
• Commitment to Accurate Diagnosis: We are dedicated to providing timely and precise diagnostic insights to support optimal patient management and care.