Confirm suspected HbS, HbC, or HbE variants.
- Patient Preparation
- Lavender (EDTA), pink (K2EDTA), or yellow (ACD Solution A or B).
- Specimen Preparation
- Transport 3 mL whole blood. (Min: 1 mL)
- Storage/Transport Temperature
- Unacceptable Conditions
- Ambient: 72 hours; Refrigerated: 1 week; Frozen: Unacceptable
Characteristics: Sickle cell disease results in vascular occlusion and tissue ischemia, and acute or chronic organ dysfunction. Milder forms present with hemolytic anemia.
Incidence: Sickle cell affects 1 in 250-600 African-Americans. HbS causes 60 to 70 percent of sickle cell disease in the United States (1 in 2000 individuals). Carrier frequency of HbS is 8-10 percent in African-Americans. HbS is common in sub-Saharan Africa, India, and the Middle East. HbC is common in West Africa. HbE is common in Southeast Asia.
Inheritance: Autosomal recessive.
Cause: Beta globin gene (HbB) missence mutations. The three detected mutations, HbS, HbC, and HbE, have one amino acid change in the beta globin chain. While HbS and HbC result in abnormal beta chain structure, the HbE mutation affects splicing efficiency, resulting in decreased amounts of beta chain.
Mutations Tested: c.19G>A (HbC), c.20A>T (HbS), c.79G>A (HbE).
Clinical Sensitivity: Greater than 70 percent for sickle cell disease; other hemoglobinopathies vary depending upon patient's ethnicity.
Methodology: PCR and fluorescence resonance energy transfer.
Analytic Sensitivity: Greater than 99 percent.
Limitations: Mutations other than c.19G>A (HbC), c.20A>T (HbS), c.79G>A (HbE) will not be detected. Diagnostic errors can occur due to rare sequence variations.
Counseling and informed consent are recommended for genetic testing. Consent forms are available online.
|Component Test Code*||Component Chart Name||LOINC|
|0051423||Beta Globin Gene Allele 1||55241-4|
|0051424||Beta Globin Gene Allele 2||55242-2|
|0051425||Beta Globin (HbS,C,E) Interpretation||21689-5|
|2001314||Beta Globin (HbS, C, E) Specimen||31208-2|
- HbS, HbC, HbE muation testing