CPT® Code 85557

The CPT® Code 85557 refers to a laboratory test known as osmotic fragility of red blood cells (RBCs) that is performed under incubated conditions. This test is designed to assess the fragility of RBCs, which is their tendency to undergo hemolysis, or rupture, when subjected to osmotic stress. In this procedure, RBCs are exposed to a hypotonic saline solution, which causes water to enter the cells. As the cells swell and reach their maximum capacity, they become increasingly susceptible to rupture. This test is particularly useful in diagnosing conditions such as hereditary spherocytic hemolytic anemia, where the RBCs are spherically shaped and have a reduced ability to expand, leading to their rupture under less severe hypotonic conditions. The results of the osmotic fragility test are interpreted based on the degree of hemolysis observed at various concentrations of sodium chloride (NaCl). A positive result is indicated when hemolysis occurs in three or more specific NaCl concentrations, which include 0.50 g/dl, 0.60 g/dl, 0.65 g/dl, and 0.75 g/dl. Additionally, the test can reveal increased fragility in conditions such as immunohemolytic anemia, following recent blood transfusions, and in various hemolytic disorders, including congenital nonspherocytic hemolytic anemia due to glucose-6-phosphate dehydrogenase (G-6-PD) deficiency or pyruvate kinase deficiency. Conversely, decreased fragility may be observed in patients who have undergone splenectomy or those with chronic liver disease, iron deficiency anemia, thalassemia, hyponatremia, polycythemia vera, and sickle cell disease. The test requires a blood sample, which is obtained through a separate venipuncture, and the analysis is conducted using techniques such as spectrophotometry or osmotic lysis-flow cytometry.