In addition to performing hemoglobin electrophoresis, a solubility test may be performed to detect the presence of what hemoglobin?

In addition to performing hemoglobin electrophoresis, a solubility test may be performed to detect the presence of what hemoglobin?

• A. A1
• B. C
• C. F
• D. S

Answer: (D)

The test is used to screen for hemoglobin S, the variant responsible for sickle cell disease. When hemoglobin is deoxygenated in the solubility test, Hb S tends to polymerize and form insoluble aggregates, making the solution turbid or visibly precipitate. This insolubility is what the test detects. Normal adult hemoglobin (Hb A) does not polymerize under these conditions, so it remains soluble. The same goes for Hb C and Hb F—they do not form the insoluble polymers in this assay, so they do not produce a positive result. Therefore, a positive solubility test points to the presence of Hb S, while the others would not cause a positive test.

The test is used to screen for hemoglobin S, the variant responsible for sickle cell disease. When hemoglobin is deoxygenated in the solubility test, Hb S tends to polymerize and form insoluble aggregates, making the solution turbid or visibly precipitate. This insolubility is what the test detects. Normal adult hemoglobin (Hb A) does not polymerize under these conditions, so it remains soluble. The same goes for Hb C and Hb F—they do not form the insoluble polymers in this assay, so they do not produce a positive result. Therefore, a positive solubility test points to the presence of Hb S, while the others would not cause a positive test.