β globin chain amino acid substitution in the 6th position from glutamic acid (Glu) to valine (Val). Only one β globin genes is affected.1,2
Heterozygous state where one normal β globin gene and one affected β globin gene are inherited.3
Due to the presence of Hb A and reduced concentration of HB S, polymerization of Hb S and sickling of red blood cells does not normally occur. As a result, condition is mostly benign and asymptomatic.
Sickling can still occur under extremely low hypoxic conditions.
All parameters (Even Hb) are normal
Absence of sickle cells
PBS appears normal
(may see a slight increase in target cells)
Hb S: 35-45%
Hb A: 50-65%
Hb A2: Normal
Hb F: Normal
Hb A:Hb S is ~60:40
Solubility Screen: Positive
Metasulfite Sickling Test: Positive
1. Laudicina RJ. Hemoglobinopathies: qualitative defects. In: Clinical laboratory hematology. 3rd ed. New Jersey: Pearson; 2015. p.231–50.
2. Harmening DM, Yang D, Zeringer H. Hemolytic anemias: extracorpuscular defects. 5th ed. Philadelphia: F.A. Davis Company; 2009. p. 250-79).
3. Randolph TR. Hemoglobinopathies (structural defects in hemoglobin). In: Rodak’s hematology clinical applications and principles. 5th ed. St. Louis, Missouri: Saunders; 2015. p. 426-453.