Blood tests in<unk>  show changes consistent with intravascular hemolytic anemia: low hemoglobin, raised lactate dehydrogenase, raised bilirubin (a breakdown product of hemoglobin), and decreased levels of haptoglobin; there can be raised reticulocytes (immature red cells released by the bone marrow to replace the destroyed cells) if there is no iron deficiency present. The direct antiglobulin test (DAT, or direct Coombs' test) is negative, as the hemolysis of<unk>  is not caused by antibodies. If the<unk>  occurs in the setting of known (or suspected) aplastic anemia, abnormal white blood cell counts and decreased platelet counts may be seen at this. In this case, anemia may be caused by insufficient red blood cell production in addition to the hemolysis. Historically, the sucrose lysis test, in which a patient's red blood cells are placed in low-ionic-strength solution and observed for hemolysis, was used for screening. If this was positive, the Ham's acid hemolysis test (after Dr Thomas Ham, who described the test in 1937) was performed for confirmation. The Ham test involves placing red blood cells in mild acid; a positive result (increased RBC fragility) indicates<unk>  or Congenital dyserythropoietic anemia. This is now an obsolete test for diagnosing<unk>  due to its low sensitivity and specificity. Today, the gold standard is flow cytometry for CD55 and CD59 on white and red blood cells. Based on the levels of these cell proteins, erythrocytes may be classified as type I, II, or III<unk>  cells. Type I cells have normal levels of CD55 and CD59; type II have reduced levels; and type III have absent levels. The fluorescein-labeled proaerolysin (FLAER) test is being used more frequently to diagnose<unk> . FLAER binds selectively to the glycophosphatidylinositol anchor and is more accurate in demonstrating a deficit than simply for CD59 or CD55. Classification<unk>  is classified by the context under which it is diagnosed: * Classic<unk> . Evidence of<unk>  in the absence of another bone marrow disorder. *<unk>  in the setting of another specified bone marrow disorder such as aplastic anemia and myelodysplastic syndrome (MDS). * Subclinical<unk> .<unk>  abnormalities on flow cytometry without signs of hemolysis.
Paroxysmal nocturnal hemoglobinuria
Paroxysmal cold hemoglobinuria
Hereditary spherocytosis
Beta thalassemia
Congenital hemolytic anemia
Hemoglobinemia
Alpha-thalassemia
Congenital dyserythropoietic anemia type II