All of the following tests are associated with the diagnosis of paroxysmal nocturnal hemoglobinuria EXCEPT which one?

The diagnosis of paroxysmal nocturnal hemoglobinuria (PNH) primarily involves tests that assess hematopoietic stem cells and the complement system, as PNH is characterized by the presence of abnormal red blood cells due to a defect in the cell membrane. Flow cytometry is a key diagnostic tool because it can detect the presence of CD55 and CD59 on the surface of red blood cells, which are often absent in PNH. Complement testing plays a role in assessing the complement-mediated hemolysis that is associated with the condition.

A bone marrow biopsy may be performed to rule out other disorders and examine hematopoiesis but is not a direct diagnostic test for PNH itself. While it can provide supportive information, it is not inherently linked to the diagnostic criteria for PNH.

The osmotic fragility test measures a red blood cell's resistance to hemolysis when placed in hypotonic solutions and is primarily used for diagnosing hereditary spherocytosis, not PNH. This specificity highlights why this test does not apply to the diagnosis of paroxysmal nocturnal hemoglobinuria. Therefore, it would not be associated with PNH diagnosis, validating the selection of this option as the correct answer.