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Information ⬇

Synonym/Acronym

Red blood cell osmotic fragility, OF.

Rationale

To assess the fragility of erythrocytes related to red blood cell (RBC) lysis toward diagnosing diseases such as hemolytic anemia.

Patient Preparation

There are no food, fluid, activity, or medication restrictions unless by medical direction.

Normal Findings

(Method: Spectrophotometry) Hemolysis (unincubated) begins at 0.5% sodium chloride (NaCl) solution and is complete at 0.3% NaCl solution. Results are compared to a normal curve.

Critical Findings and Potential Interventions ⬆ ⬇

N/A

Overview ⬆ ⬇

Study type: Blood collected in a green-top [heparin] tube and two peripheral blood smears; related body system: Circulatory/Hematopoietic system.

Osmotic fragility (OF) is an indication of the ability of RBCs to experience osmotic stress and take on water without lysing. Normal red blood cell (RBC) membranes must be flexible to changes in plasma concentrations of electrolytes and other substances. In this test, RBCs are placed in graded dilutions of NaCl. Swelling of the cells occurs at lower concentrations of NaCl as they take on water in the hypotonic solution; that is, the concentration of electrolyte is higher inside the RBC, and in order to establish equilibrium with the surrounding fluid the RBC must take on water by osmosis. Normal RBCs can absorb an increased volume; because of their biconcave shape, they have more surface area and can swell. Thicker cells, such as spherocytes, have an increased OF because they are already spherical, already have weak membranes, and cannot take on more volume without lysing; thinner cells have a decreased OF.

Indications ⬆ ⬇

Evaluate hemolytic anemia.

Interfering Factors ⬆ ⬇

Factors That May Alter the Results of the Study

  • Drugs and other substances that may increase osmotic fragility include dapsone.
  • Parasitic infestations, such as malaria, may independently cause cell hemolysis.

Other Considerations

  • Specimens should be submitted for analysis immediately after collection.

Potential Medical Diagnosis: Clinical Significance of Results ⬆ ⬇

Increased In

Conditions that produce RBCs with a small surface-to-volume ratio or RBCs that are rounder than normal will have increased osmotic fragility.

Decreased In

Conditions that produce RBCs with a large surface-to-volume ratio or RBCs that are flatter than normal will have decreased osmotic fragility.

Nursing Implications, Nursing Process, Clinical Judgement ⬆

Before the Study: Planning and Implementation

Teaching the Patient What to Expect

  • Discuss how this test can assist in assessing for anemia.
  • Explain that a blood sample is needed for the test.
  • Discuss symptoms of anemia: chest pain, dizziness, fatigue, hands and feet that feel cold, headache, irregular pulse, pale skin, shortness of breath, and weakness; additional symptoms of hemolytic anemia include jaundice (related to the accumulation of excessive amounts of bilirubin in the sclera and skin) and development of gall stones (related to abnormal elevations of bilirubin in the bile, which may lead to formation of gallstones).

After the Study: Implementation & Evaluation Potential Nursing Actions

Treatment Considerations

  • Monitor and trend bilirubin, Hgb/Hct, and RBC count.
  • Observe the patient for development of jaundice.
  • Explain that RBC transfusion(s) may be ordered to treat the anemia.
  • Note that splenectomy may be performed in the presence of significant anisocytosis (variations in RBC size) and/or poikilocytosis (variations in RBC shape) to reduce massive splenic destruction of the abnormal RBCs which would lead to anemia.

Clinical Judgement

  • Consider ways to provide culturally appropriate information related to potential blood transfusion.

Follow-Up and Desired Outcomes

  • Acknowledges that additional testing may be necessary to monitor disease progression or evaluate the need for a change in therapy.