Diagnostic Test Directory

Molecular Genetics Laboratory

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Sickle Cell Anemia (HBB)

  • Synonyms: Sickle Cell Trait, Sickle-Beta thalassemia, Beta globin gene sequence analysis
  • LIS Mnemonic: MBSS

    Collect

    Collect whole blood in a purple top (EDTA) tube (preferred). Extracted DNA is also acceptable

    Volume Required

    5 ml whole blood or 1 ug extracted DNA

    Minimum Required

    3 ml whole blood

    Transport

    Refrigerate sample until shipment. Send the sample at room temperature with overnight delivery for receipt Monday through Friday within 24 hours of collection.

    Stability

    Whole blood can be refrigerated until shipment.

    Unacceptable conditions

    Heparinized specimens, severely hemolyzed specimens, frozen, clotted or possibly commingled specimens, blood in non-sterile or leaky containers, mislabeled or inappropriately labeled specimens.

    Specimen Handling

    Do not heat, freeze or centrifuge blood before shipment. Refrigerate sample until shipment.

Days Performed

Mon - Fri 9:00am to 4:00pm

Reported

2-3 weeks

CPT

81401

Disease Information

Clinical Features:

Beta thalassemia is characterized by severe anemia, growth retardation, splenomegaly, bone changes with characteristic facies and iron depositions affecting cardiac and endocrine systems. Beta thalassemia is characterized by hypochromic, hemolytic anemia and dependence on blood transfusions to sustain life. Even with chelation therapy to remove excess iron stores, the life expectancy in classic beta thalassemia major is shortened to 25-30 years on average. It has been estimated that 3% of the world’s population carries a beta thalassemia gene. These carriers, individuals with beta thalassemia trait, are essentially normal, although they can be detected by lowered mean corpuscular volume (MCV) typically <80fl, lowered mean corpuscular hemoglobin value (MCH) typically <26-34 pg/rbc and an elevated A2 level, typically 4.5-6.0. Determination of these values as well as ethnicity are very useful in diagnosis and should be obtained whenever possible.

Molecular Genetics:

The HBB gene is located on chromosome 11p15.5. The inheritance pattern is autosomal recessive. Beta thalassemia is caused by decreased or absent ß-globin chain production. The sickle cell mutations are found at codon 7 (HbS and HbC) while beta thalassemia mutations are found throughout the gene.

Test Methods:

We offer DNA sequence analysis for sickle cell (HbS) mutations which are detected by sequencing the beta globin coding region and part of the intervening sequences. Sequence variants are classified as mutations, variants of unknown significance or benign variants unrelated to disease. Variants of unknown significance may warrant further studies in the patient and other family members.

Detection Rate:

This assay will detect over 100% of HbS and HbC alleles. The analytical sensitivity is close to 100%.

Results:

Test results with interpretation will be mailed and/or faxed to the referring physician or send out lab following completion of the test. Additional reports will be provided as requested.

Utility:

The clinical utility of the assay is to confirm a diagnosis of sickle cell disease; identify carriers sickle cell trait and to facilitate prenatal testing and counseling for reproductive risk.

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215-590-5221