Anticoagulant used for osmotic fragility test
**Core Concept**
The osmotic fragility test is a laboratory procedure used to assess the resistance of red blood cells to hemolysis (breakdown) in hypotonic solutions. This test is crucial in diagnosing hereditary spherocytosis, a genetic disorder characterized by abnormally shaped red blood cells.
**Why the Correct Answer is Right**
The anticoagulant used in the osmotic fragility test is sodium citrate. Sodium citrate works by chelating calcium ions, which are essential for the coagulation cascade. By binding to calcium, sodium citrate effectively inhibits the coagulation process, allowing the test to proceed without clot formation. This is particularly important in the osmotic fragility test, where the red blood cells are subjected to varying concentrations of salt solutions, and any clotting would interfere with the results.
**Why Each Wrong Option is Incorrect**
* **Option A:** Sodium fluoride is incorrect because it inhibits glycolysis, which is not relevant to the osmotic fragility test.
* **Option B:** Heparin is incorrect because it is an anticoagulant that works by activating antithrombin III, which is not the mechanism used in the osmotic fragility test.
* **Option C:** EDTA (ethylenediaminetetraacetic acid) is incorrect because it is a chelating agent that binds to multiple metal ions, including calcium, but it is not the preferred anticoagulant for the osmotic fragility test.
**Clinical Pearl / High-Yield Fact**
When performing the osmotic fragility test, it is essential to use sodium citrate as the anticoagulant to prevent clotting and ensure accurate results.
**Correct Answer:** A. Sodium citrate