CPT® Code 85555

The CPT® Code 85555 refers to a laboratory test that assesses the osmotic fragility of red blood cells (RBCs) in an unincubated state. Osmotic fragility is a critical measure of how susceptible red blood cells are to hemolysis, which is the process of rupture or destruction of these cells when they are subjected to osmotic stress. In this test, red blood cells are exposed to hypotonic saline solutions, which causes water to enter the cells. As the cells swell from the influx of fluid, they eventually reach a point where they can no longer withstand the pressure and rupture. This test is particularly useful in diagnosing conditions such as hereditary spherocytic hemolytic anemia, where the red blood cells are abnormally shaped (spherocytes) and have a reduced capacity to expand. Consequently, these spherocytic cells are more likely to hemolyze under less extreme hypotonic conditions compared to normal red blood cells. The results of the unincubated osmotic fragility test can indicate positive results when hemolysis is observed in three or more specific concentrations of sodium chloride (NaCl). Additionally, the test can reveal increased fragility in various hemolytic disorders, recent blood transfusions, and specific anemias, while decreased fragility may be noted in conditions such as post-splenectomy and chronic liver disease. The test is performed on a blood sample obtained through venipuncture, and the analysis is conducted using techniques such as spectrophotometry or osmotic lysis-flow cytometry.