mjl1717
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What is a sugar/ water test used for?
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| kalsam
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blood test to detect increased fragility of red blood cells by swelling them in low-salt solution
This test is ordered for suspected paroxysmal nocturnal hemoglobinuria (PNH), and for any hemolytic anemia of unkown origin.
When a low-salt solution containing sucrose (sugar) is added to these cells, the complement is activated, binds to the cells, and bursts them.
Normal Values
negative: less than 5% hemolysis (red blood cell breakdown)
positive: greater than 10% hemolysis
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| Sakaki-
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I think that this refers the sucrose hemolysis test...which should detect the increased susceptibility of PNH RBCs to complement lysis (rather than osmotic fragility).
The osmotic fragility test uses varying solutions of differing salt concentrations (rather than sucrose).
The sucrose hemolysis test used as a screen for PNH provides a low ionic strength solution that promotes the binding of complement to the red cell membranes. The defective ones in PNH (missing DAF, MIRL, or HRF) lyse. The correct reference ranges were listed above (with positive being >10% hemolysis).
If positive, this is followed by Ham's test to confirm PNH, which uses acidified serum (which activates complement as well). In this test, positivity is indicated by hemolysis enhanced by acidified serum and hemolysis not occurring in the presence of heated serum (which inactivates the complement).
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