Hemoglobin (Hb) Solubility

False-positive solubility test for sickling may be due to polycythemic blood; interference by some forms of hyperglobulinemia; and a variety of abnormal hemoglobins, including I, Bart, C_Georgetown, Alexandra, C_Harlem, Porto Alegre, Memphis/S, C_Ziguinchor, and S_Travis.¹ Positive tests should be confirmed by hemoglobin fractionation. A positive reaction also occurs in the presence of many Heinz bodies (eg, after splenectomy), and in blood protein disorders due to precipitation of plasma proteins. False-negative solubility test reactions may occur with inadequate quantities of blood from anemic patients (hemoglobin levels <8.0 g/dL); high concentration of Hb F or of phenothiazines may inhibit the sickle reaction;¹ quantities of hemoglobin S too small to detect, as at birth or with transfusions of nonhemoglobin S into patients with hemoglobin S. The appearance of hemoglobin S is genetically delayed and is not present in sufficient quantity until after three months of age. Maximum levels are not reached until about six months of age. Solubility tests are unlikely to be reliably positive until after six months of age; therefore, this test should not be used for testing neonates or children younger than six months of age.