PNH confirmation test, Blood

Blood

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Flow cytometry for GPI-anchored proteins.

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PNH Confirmation Test Blood - Comprehensive Medical Guide

Why is it done?
- Detects paroxysmal nocturnal hemoglobinuria (PNH), a rare acquired disorder characterized by deficiency of complement regulatory proteins (CD55 and CD59) on blood cell surfaces
- Confirms diagnosis in patients with suspected PNH presenting with hemolytic anemia, thrombosis, or bone marrow failure
- Screens for PNH in patients with unexplained hemolysis, thrombophilia, or aplastic anemia
- Evaluates patients with hemoglobinuria or dark urine of unclear etiology
- Typically performed when initial screening tests suggest PNH or in patients with clinical symptoms consistent with the disease
Normal Range
- Normal: >99% of blood cells (granulocytes, monocytes, and red blood cells) express CD55 and CD59 proteins on their surface
- Positive PNH test: Detectable absence or significant reduction (<50%) of CD55 and/or CD59 on blood cells, typically measured by flow cytometry as percentage of affected cells
- Classification: Classic PNH (≥50% abnormal cells) or Small PNH clone (<50% abnormal cells); PIG-A gene mutation present in affected cells
- Units: Percentage of abnormal cells; specific markers assessed via flow cytometry (CD55-FITC, CD59-PE, or similar fluorescent antibodies)
- Normal results indicate absence of PNH; abnormal results confirm deficiency of GPI-anchored complement regulatory proteins and establish PNH diagnosis
Interpretation
- Negative result: Normal CD55/CD59 expression (>99% cells); rules out PNH; suggests alternative diagnoses for presenting symptoms
- Positive result: Detectable deficiency of CD55 and/or CD59; confirms PNH diagnosis; severity correlates with percentage of abnormal cells and clinical manifestations
- Small PNH clone (5-50% abnormal cells): May present with subclinical disease; risk of thrombosis and hemolysis present; requires monitoring even if asymptomatic
- Classic PNH (>50% abnormal cells): Symptomatic disease likely; significant risk of intravascular hemolysis, thrombotic events, and cytopenias; requires active management
- Severity assessment: Different cell lineages (granulocytes, monocytes, RBCs) may show varying degrees of abnormality; provides prognostic information
- Factors affecting interpretation: Recent transfusion, immunosuppressive therapy, aplastic anemia overlap, and evolution of PNH clone over time
Associated Organs
- Primary system: Hematopoietic system (bone marrow, blood cells); complement system dysfunction affects all blood cell lineages
- Hemolytic anemia: Intravascular and extravascular hemolysis due to uncontrolled complement activation on red blood cells; results in jaundice, hemoglobinuria, and anemia
- Thrombosis complications: Increased risk of venous and arterial thrombosis (35-40% of patients); affects cerebral, hepatic, portal, and mesenteric vessels
- Bone marrow: Cytopenias (anemia, thrombocytopenia, leukopenia); increased risk of aplastic anemia; PNH often coexists with myelodysplasia
- Liver: Budd-Chiari syndrome (hepatic vein thrombosis); portal vein thrombosis; hepatic complications in 5-10% of PNH patients
- Central nervous system: Cerebral venous sinus thrombosis; stroke risk; neurological complications associated with thrombotic disease
- Kidney: Renal infarction; renal dysfunction secondary to hemolysis; acute kidney injury from hemoglobinuria
- Associated conditions: Aplastic anemia, myelodysplastic syndrome, immune thrombocytopenia, acquired bone marrow failure syndromes
Follow-up Tests
- Complete blood count (CBC): Monitor hemoglobin, hematocrit, platelet count, and white blood cell count for cytopenias and hemolysis
- Reticulocyte count: Assess bone marrow response to hemolysis; elevated levels indicate active hemolysis
- Lactate dehydrogenase (LDH): Elevated in hemolysis; marker of disease activity and severity
- Bilirubin (total and indirect): Elevated in hemolysis; indirect hyperbilirubinemia indicates red cell destruction
- Haptoglobin level: Low in intravascular hemolysis; consumed by hemoglobin binding
- Urinalysis: Screen for hemoglobinuria and hemosiderin; indicates severity of intravascular hemolysis
- Direct antiglobulin (Coombs) test: Negative in PNH; helps exclude autoimmune hemolytic anemia
- Coagulation studies (PT, PTT, D-dimer, fibrinogen): Screen for thrombosis risk and coagulopathy
- Imaging studies: Ultrasound or CT imaging to evaluate for thrombotic complications (hepatic vein, portal vein, cerebral vessels)
- Flow cytometry for PIG-A mutation analysis: Confirms clonal origin of abnormal cells
- Bone marrow examination: If concurrent aplastic anemia or myelodysplasia suspected
- Renal function tests: Monitor for kidney involvement and hemoglobin-related renal injury
- Repeat flow cytometry: Monitor disease progression and treatment response; recommended at 6-12 month intervals
Fasting Required?
- No - Fasting is not required for PNH confirmation test blood
- Special instructions: No specific preparation required; patient can eat and drink normally
- Medications: Continue regular medications unless otherwise directed by physician; anticoagulants and antiplatelet agents do not interfere with test
- Sample collection: Blood sample obtained via venipuncture into EDTA tube (purple-top) or specific flow cytometry tubes; requires 2-3 mL
- Timing considerations: Sample should be processed within 24 hours of collection for optimal results; flow cytometry analysis requires fresh or properly preserved blood
- Patient preparation: No special preparation needed; wear comfortable, loose-fitting clothing to facilitate venipuncture; remain calm and relaxed
- Recent transfusion: Inform laboratory if patient received blood transfusion recently, as donor cells may affect interpretation; recommend waiting 3-4 days post-transfusion if possible

How our test process works!