Sickledex Tests With Unstable Hemoglobin Disorders

To the Editor.—  In the article by Nalbandian and co-workers entitled "Sickledex Test for Hemoglobin S: A Critique" (218:1679-1680, 1971), it is stated that false-positive results may be given by "... non-S sickling hemoglobins such as C_Harlem... and Heinz-body-forming hemoglobins." Some readers may interpret this statement to mean that the "Heinz-body-forming hemoglobins" both sickle and give positive Sickledex tests. To ascertain whether this is correct, we have examined blood specimens from four patients with unstable hemoglobin disorders: one patient with hemoglobin H disease, two with hemoglobin Köln disease (α₂β₂^{98 valine}), and one with hemoglobin Olmsted disease (α₂β₂^{141 arginine}). Sickle cell tests with 2% sodium metabisulfite were negative in each case. The saponin-dithionite turbidity test as specified by Nalbandian et al gave normal results in the patient with hemoglobin H disease and in both patients with hemoglobin Köln disease; however, the test