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Test ID: FRAG
Osmotic Fragility, Erythrocytes

Useful For Suggests clinical disorders or settings where the test may be helpful

Suspected hereditary spherocytic hemolytic anemia

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Spherocytes are osmotically fragile cells that rupture more easily in a hypotonic solution than do normal RBCs. Because they have a low surface area:volume ratio, they lyse at a higher osmolarity than do normal discocyte (RBCs). Cells that have a larger surface area: volume ratio, such as target cells or hypochromic cells are more resistant to lysing. After incubation, an increase in hemolysis is seen in hereditary spherocytosis.

 

The test is helpful in confirming or detecting mild spherocytosis.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

0.50 g/dL NaCl (unincubated)

Males: 0.0-47.8% hemolysis

Females: 0.0-31.1% hemolysis

 

0.60 g/dL NaCl (incubated)

Males: 18.7-67.4% hemolysis

Females: 10.9-65.5% hemolysis

 

0.65 g/dL NaCl (incubated)

Males: 4.4-36.6% hemolysis

Females: 0.2-39.3% hemolysis

 

0.75 g/dL NaCl (incubated)

Males: 0.8-9.1% hemolysis

Females: 0.0-10.9% hemolysis

Interpretation Provides information to assist in interpretation of the test results

Increased lysis in 3 or more concentrations of sodium chloride indicates increased red cell fragility.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Infrequently, other hemolytic disorders may also be associated with positive results, as in patients with congenital nonspherocytic hemolytic anemia due to glucose-6-phosphate dehydrogenase or pyruvate kinase deficiency.

 

Patients with an immunohemolytic anemia, or who have recently received a blood transfusion may also have increased RBC lysis.

Clinical Reference Provides recommendations for further in-depth reading of a clinical nature

Palek J, Jarolin P: Hereditary spherocytosis. In Hematology. 4th edition. Edited by WJ Williams, E Beutler, AJ Erslev, MA Lichtman. New York, McGraw-Hill Book Company, 1990, pp 558-569