Hi-Sickle Kit (Solubility Test for detection of Hemoglobin 'S')

Human hemoglobin is formed from two pairs of globin chains each with a heme group attached. The binding of a heme group into the heme pocket in each chain is vital for the oxygen- carrying capacity of the molecule and stabilizes the whole molecule. Alterations in the structure of hemoglobin are usually brought about by point mutations that affect the coding for amino acids in the globin chains. In sickle cell anemia, a point mutation (GAG to GTG) in the ß- chain at codon position 6 results in the encoding of a valine instead of normal glutamine. The resulting abnormal ß- chains combine with normal ßchains to form abnormal hemoglobin S (HbS). HbS is poorly soluble in low oxygen tension situations forming a gel and polymerizing into fibrilary structures or tactoids. This distorts the red blood cells causing them to become rigid and sickled.

Individuals with sickle cell anemia (Homozygous S/S) may have early mortality with vascular occlusions of multiple organ system, severe hemolytic anemia and hypoxia. Individuals with sickle cell trait (Heterozygous A/S) are usually asymptomatic. However, under certain conditions of reduced oxygen tension such as hypoxia during anesthesia, flight in poorly pressurized airplanes, severe pneumonia, these individuals can experience a sickle cell crisis.

This kit is based on the solubility difference between HbS and HbA in Solubility Test Reagent. When red cells are introduced into such a solution, they lyse immediately. The hemoglobin released from the lysed red cells, is reduced by Reagent Mix provided with the kit. This reaction causes precipitation of HbS leading to turbidity of the reaction mixture. However, HbA, as well as other hemoglobins are soluble leading to clarity in the reaction mixture.