Osmotic Fragility Test

Blood

Report in 48Hrs

At Home

No Fasting Required

Details

RBC fragility test.

₹1,021₹1,459

30% OFF

Osmotic Fragility Test - Comprehensive Medical Information Guide

Why is it done?
- Test Purpose: The osmotic fragility test measures the ability of red blood cells (RBCs) to withstand hypotonic solutions. It evaluates the structural integrity and osmotic resistance of erythrocytes by exposing them to progressively dilute saline solutions and determining at what osmolarity the cells begin to lyse (hemolysis).
- Primary Indications: Detection of hereditary spherocytosis and other membrane disorders causing abnormal RBC fragility
- Investigation of hemolytic anemias with suspected RBC membrane abnormalities
- Differentiation between hereditary and acquired hemolytic conditions
- Evaluation of patients with unexplained anemia and jaundice
- Clinical Timing: Typically performed when peripheral blood smear shows spherocytes, when family history of hemolytic anemia is present, or when other hemolytic markers are elevated
- Often performed as part of a diagnostic workup for chronic hemolysis or unexplained splenomegaly
Normal Range
- Normal Range Values: Measured as osmolality in mOsm/kg or concentration as NaCl percentage
- Initial Hemolysis: 300-325 mOsm/kg (approximately 0.48% NaCl solution) - the osmolality at which hemolysis first becomes visible
- Complete Hemolysis: 195-215 mOsm/kg (approximately 0.30% NaCl solution) - the osmolality at which 100% of RBCs are lysed
- 50% Hemolysis Point: 250-260 mOsm/kg (approximately 0.35-0.36% NaCl) - the midpoint of hemolysis often used for comparison
- Interpretation of Results:
- Normal/Negative: RBCs hemolyze at expected osmolalities; RBCs have normal membrane integrity and osmotic resistance
- Increased Fragility (Shift to Higher Osmolalities): RBCs hemolyze at higher osmolalities (less dilute solutions); indicates abnormally fragile cells; characteristic of hereditary spherocytosis
- Decreased Fragility (Shift to Lower Osmolalities): RBCs resist hemolysis at lower osmolalities (more dilute solutions); seen in thalassemia, iron deficiency anemia, and other conditions with abnormal RBC morphology
- Bimodal Pattern: Two distinct populations of RBCs with different fragility; may indicate mixed RBC populations
Interpretation
- Increased Osmotic Fragility (Positive Test):
- Indicates RBCs are more fragile than normal and lyse at higher osmolalities Most commonly associated with hereditary spherocytosis (HS), the primary indication for this test Reflects spherical cell shape which reduces surface area-to-volume ratio May also indicate autoimmune hemolytic anemia (AIHA) where antibody-coated cells show increased fragility Can occur in severe burns or thermal injury where RBCs are damaged More pronounced when tested on older blood samples or after incubation
- Decreased Osmotic Fragility (Negative Test):
- RBCs are more resistant to hemolysis than normal Characteristic of hypochromic anemias including iron deficiency anemia and thalassemia Associated with target cells (codocytes) that have increased surface area-to-volume ratio Seen in polycythemia vera where RBCs are more abundant May occur in liver disease with target cell formation Can be present in post-splenectomy patients with target cells
- Normal Osmotic Fragility:
- Rules out membrane-related hemolytic anemias as primary diagnosis Does not exclude other causes of hemolysis May still see hemolysis from other mechanisms (immune, enzymatic, infection-related)
- Factors Affecting Results:
- Sample age: Older samples may show increased fragility due to RBC deterioration Temperature: Incubation at 37°C may increase fragility compared to room temperature pH: Acidic conditions may alter RBC membrane properties Presence of spherocytes on smear supports increased fragility interpretation Reticulocytosis: Young RBCs may have different fragility characteristics Patient medications affecting RBC function Recent transfusion: Donor RBCs may have different characteristics
- Clinical Significance:
- Helps differentiate hereditary membrane disorders from other hemolytic anemias Valuable in confirming hereditary spherocytosis diagnosis when combined with other tests Guides treatment decisions: HS patients may benefit from splenectomy Helps counsel patients regarding hereditary nature of condition Important for identifying carriers in familial HS
Associated Organs
- Primary Organ System: Hematologic System (blood and bone marrow)
- Secondary Organs Affected:
- Spleen: Primary site of sequestration and destruction of osmotically fragile RBCs; may become enlarged (splenomegaly)
- Liver: May become enlarged; involved in reticuloendothelial clearance of damaged RBCs; bilirubin metabolism affected by hemolysis
- Bone Marrow: Compensatory erythropoiesis occurs to maintain adequate RBC count despite ongoing hemolysis
- Gallbladder: May develop pigment gallstones from chronic bilirubin elevation
- Kidneys: May be affected by hemoglobinuria in severe hemolysis
- Associated Medical Conditions:
- Hereditary Spherocytosis (HS): Primary disorder for which this test is indicated; caused by mutations in genes encoding RBC membrane proteins (spectrin, ankyrin, band 3, protein 4.2); autosomal dominant or recessive inheritance
- Autoimmune Hemolytic Anemia (AIHA): May show increased osmotic fragility; caused by antibodies against RBC antigens
- Thalassemia Major and Minor: Show decreased osmotic fragility due to target cell formation
- Iron Deficiency Anemia: Results in target cells and decreased osmotic fragility
- Liver Disease: Cirrhosis and hepatic dysfunction cause target cell formation and decreased fragility
- Pyruvate Kinase Deficiency: Glycolytic enzyme deficiency causing hemolytic anemia with possible osmotic fragility changes
- Potential Complications of Abnormal Results:
- Chronic hemolysis with resulting anemia Jaundice and hyperbilirubinemia Gallstone formation (cholelithiasis) Splenic infarction from RBC sequestration Aplastic crisis (particularly in hereditary spherocytosis) Growth retardation in children with chronic hemolysis Iron overload from chronic transfusions if needed Leg ulcers from chronic hemolysis (in some hereditary hemolytic anemias)
Follow-up Tests
- Recommended Follow-up Tests Based on Results:
- Incubated Osmotic Fragility Test: Blood sample is incubated at 37°C for 24 hours before testing; enhances detection of hereditary spherocytosis; may show abnormalities when fresh sample appears borderline
- Peripheral Blood Smear: Directly visualize RBC morphology for spherocytes, target cells, and other abnormalities; confirms suspected diagnosis from osmotic fragility results
- Complete Blood Count (CBC): Assesses hemoglobin level, hematocrit, RBC indices (MCV, MCH, MCHC), white blood cell and platelet counts; determines degree of anemia; evaluates reticulocyte count
- Reticulocyte Count: Measures immature RBCs; elevated in hemolytic anemias indicating increased RBC production; important marker of hemolysis severity
- Lactate Dehydrogenase (LDH): Elevated when RBCs are destroyed; marker of hemolysis severity; LDH-1 greater than LDH-2 pattern suggests hemolysis
- Bilirubin (Total and Direct): Elevated unconjugated bilirubin indicates hemolysis; helps quantify severity of hemolysis
- Haptoglobin: Significantly decreased or absent in hemolytic anemias; haptoglobin binds to free hemoglobin released from lysed RBCs
- Direct Coombs Test (DAT): Detects antibodies bound to RBC surface; positive in autoimmune hemolytic anemia; helps differentiate from hereditary conditions
- Eosin-5-Maleimide (EMA) Binding Test: Flow cytometry-based test for hereditary spherocytosis; binds to band 3 protein; more specific than osmotic fragility for HS diagnosis
- Hemoglobin Electrophoresis: Performed if hemoglobinopathy suspected; identifies abnormal hemoglobin variants including thalassemia variants
- RBC Membrane Protein Analysis: Advanced testing using SDS-PAGE electrophoresis; identifies specific protein abnormalities in hereditary spherocytosis
- Genetic Testing: DNA sequencing to identify mutations in HS-related genes; used for definitive diagnosis and family screening
- Glucose-6-Phosphate Dehydrogenase (G6PD) Screening: Performed if enzymatic hemolytic anemia suspected; screens for G6PD deficiency
- Monitoring Frequency:
- For newly diagnosed hereditary spherocytosis: baseline testing followed by periodic monitoring (annually or as clinically indicated) For documented HS patients: monitor hemoglobin and reticulocyte count regularly to assess disease stability Post-splenectomy: regular monitoring to assess adequacy of symptom relief and hemoglobin stability During acute hemolytic episodes: more frequent testing (weekly or more often) to track severity Family members of HS patients: one-time screening if clinical suspicion exists
Fasting Required?
- Fasting: No
- Explanation: Fasting is NOT required for the osmotic fragility test. The test measures physical properties of RBCs and is not affected by nutritional intake or recent food consumption.
- Patient Preparation Requirements:
- Timing of Blood Draw: Can be drawn at any time of day; no specific time restrictions apply
- Sample Collection: Venipuncture into EDTA tube (lavender/purple top) for anticoagulated whole blood Approximately 3-5 mL of blood required Proper mixing of blood with anticoagulant is essential Sample should be gently mixed to avoid hemolysis before testing
- Sample Handling: Test should be performed as soon as possible after collection (ideally within 4 hours) Store at room temperature if processing delayed Do not refrigerate or freeze the sample as this may affect RBC osmotic properties Avoid extreme temperatures during transport
- Medications: No specific medications need to be held or discontinued for this test Medications affecting RBC survival or hemolysis should be noted by healthcare provider Continue regular medications unless otherwise instructed Inform laboratory of medications that may affect test results (immunosuppressants, corticosteroids in AIHA patients)
- Special Considerations:
- Recent transfusion: If patient recently received blood transfusion, inform laboratory as donor RBCs may affect results Severe infection or stress: May temporarily alter RBC properties Pregnancy: May affect RBC indices and osmotic fragility High altitude residence: May affect hematologic parameters Recent blood loss: Patient should be stable hemodynamically Hemolytic episode: Test may be more informative if performed during acute hemolysis

How our test process works!