Sugar-water hemolysis test

Definition:

The sugar-water hemolysis test is a blood test to detect fragile red blood cells by testing their ability to withstand swelling in a low-salt solution.

Alternative Names:

Sucrose hemolysis test

How the test is performed:

A blood sample is needed. For information on how this is done, see: Venipuncture

How to prepare for the test:

There is no special preparation needed for this test.

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:

Your doctor may order this test if you have signs or symptoms of paroxysmal nocturnal hemoglobinuria (PNH) or hemolytic anemia of unknown cause. PNH red blood cells are very likely to be harmed by the body's complement system.

Normal Values:

Negative: less than 5% red blood cell breakdown (hemolysis)
Positive: more than 10% hemolysis

The examples above are common measurements for results of these tests. Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples.Talk to your doctor about the meaning of your specific test results.

What abnormal results mean:

Paroxysmal nocturnal hemoglobinuria (PNH)
Autoimmune hemolytic anemias and leukemia may give false positive result

What the risks are:

There is very little risk involved with having your blood taken. Veins and arteries vary in size from one patient to another and from one side of the body to the other. Taking blood from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight but may include:

Excessive bleeding
Fainting or feeling light-headed
Hematoma (blood accumulating under the skin)
Infection (a slight risk any time the skin is broken)

Special considerations:

A negative test does not rule out PNH. False-negative results may occur if the fluid part of blood (serum) lacks complement.

References:

Brodsky RA. Paroxysmal nocturnal hemoglobinuria. In: Hoffman R, Benz EJ, Shattil SS, et al, eds. Hematology: Basic Principles and Practice. 5th ed. Philadelphia, Pa: Elsevier Churchill Livingstone; 2008:chap 30.

Schwartz RS. Autoimmune and intravascular hemolytic anemias In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 163.