41 Sickle Cell Trait (Hemoglobin AS)

Michelle To and Valentin Villatoro

Cause(s): 

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

 

Inheritance: 

Heterozygous state where one normal β globin gene and one affected β globin gene are inherited.3

 

Clinical Findings:1-3

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.

 

Laboratory Features:1-3

CBC:

All parameters (Even Hb) are normal

PBS:

Absence of sickle cells

PBS appears normal

(may see a slight increase in target cells)

BM:

N/A

Hemoglobin Electrophoresis:

Hb S: 35-45%

Hb A: 50-65%

Hb A2: Normal

Hb F: Normal

Hb A:Hb S is ~60:40

Other Tests:

Solubility Screen: Positive

Metasulfite Sickling Test: Positive

HPLC

Hemoglobin Electrophoresis


References:

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.

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A Laboratory Guide to Clinical Hematology by Michelle To and Valentin Villatoro is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License, except where otherwise noted.

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