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Sugar-waterhemolysis test
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| Definition: |
A test to detect increased fragility of red blood cells by swelling in low ionic (low salt) solution.
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| Alternative Names: |
Sucrose hemolysis test
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| How the test is performed: |
Adult or child:
Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and a tourniquet (an elastic band) or blood pressure cuff is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the tourniquet to distend (fill with blood). A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the tourniquet is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.
Infant or young child:
The area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding.
The blood is analyzed in a laboratory. |
| How to prepare for the test: |
Adults:
There is no special preparation.
Infants and children:
The physical and psychological preparation you can provide for this or any test or procedure depends on your child's age, interests, previous experience, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child's age:
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| How the test will feel: |
| When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing. |
| Why the test is performed: |
| This test is ordered for suspected paroxysmal nocturnal hemoglobinuria (PNH), and for any hemolytic anemia of obscure origin. PNH red blood cells are unusually susceptible to complement (a component of the body's defense mechanism). When a low ionic (low salt) solution containing sucrose (sugar that does not introduce an osmotic gradient) is added to a suspension of PNH red blood cells, complement is activated by the alternate pathway; it binds to red blood cells, and lyses(bursts) the cells.
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| Normal Values: |
- negative: less than 5% hemolysis (red blood cell breakdown)
- positive: greater than 10% hemolysis
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| What abnormal results mean: |
- paroxysmal nocturnal hemoglobinuria (PNH)
- autoimmune hemolytic anemias and leukemia may give false positive result
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| What the risks are: |
Risks associated with venipuncture are slight:
- excessive bleeding
- fainting or feeling light-headed
- hematoma (blood accumulating under the skin)
- infection (a slight risk any time the skin is broken)
- multiple punctures to locate veins
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| Special considerations: |
| A negative test does not rule out PNH. False-negative results may occur if the serum is depleted of complement. |
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Review Date: 10/24/2001
Reviewed By: Rebecca Elstrom, M.D., Division of Hematology-Oncology, University of Pennsylvania Medical Center, Philadelphia, PA. Review provided by VeriMed Healthcare Network.
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