Serum Haptoglobin in Hemolytic Disease

To the Editor.—  Inadequate construction of study and control groups by Marchand et al (1980;243:1909) inflates the apparent sensitivity and specificity of their serum haptoglobin assay. More important, there is no reason to believe that the test has much practical value.Classification of megaloblastic anemia with hemolytic anemias advances the hypothesis of Marchand and coworkers, but it ignores that this is a problem of decreased RBC production because of ineffective erythropoiesis (intramedullary hemolysis); the shortened RBC survival contributes little to the anemia. It is then no wonder that Marchand and associates find little correlation between reticulocytosis and hemolysis, as megaloblastic anemia occurs with absolute reticulocytopenia. The control group of nonhemolytic diseases does not include other diseases characterized by ineffective erythropoiesis, such as sideroblastic anemia and agnogenic myeloid metaplasia. In hypersplenism, a disease that is clearly hemolytic, haptoglobin levels are normal, but only two such patients were studied. These factors greatly