Clinical Diagnostics and Research tools
Sickle Solubility Test (SST)
The Sickle Solubility Test (SST) is used to screen for the presence of sickling hemoglobins. A positive result must be confirmed by another method (HPLC or electrophoresis) to confirm the presence of Hb S and to distinguish Hb AS (carrier state) from Hb SS (sickle cell disease). Other insoluble hemoglobins, such as Hb C-Harlem, will also give a positive result.
The SST utilizes a procedure based upon phosphate solubility whereby erythrocytes are lysed by saponin and the released hemoglobin is reduced by sodium hydrosulfite in a phosphate buffer. Reduced HbS is characterized by its very low solubility and the formation of neumatic liquid crystals (tactoids). The resulting tactoids of HbS or non-sickling hemoglobin (e.g. HbC-Harlem) causes the solution to remain turbid. The presence of HbA under these same conditions results in a clear red solution.
Nalbandian RM, et al. Dithionite tube test: A rapid, inexpensive technique for the detection of hemoglobin S and non-S sickling hemoglobin. Clin Chem 17:1028-1032,1971.