Beta Hemoglobin DNA Sequencing

Interpretation

Guidelines

• Genetics and Solid Tumor Diagnostic Testing

Method

DNA sequencing of the coding regions, introns, and flanking sequences of the hemoglobin beta (HBB) gene in both directions to detect point mutations causing beta globin variants and beta thalassemia.

This test sequences bidirectionally a 2 kb contiguous region of the HBB (beta globin) gene from approximately bases 61941 to 63927 of Genbank U01317, corresponding to bases minus 195 to plus 1792 relative to the start of transcription. Patient sequences are compared against Genbank U01317 as genomic reference sequence to detect mutations. Mutations are reported at the genomic level, with base 1 corresponding to the start of transcription. Mutations that change an amino acid are reported at the protein level according to the sequence of the mature protein without its initiator methionine, and may also be described by the traditional name of the hemoglobin variant.

Correspondence between this mutation nomenclature system and the HGVS nomenclature system may be found at the Globin Gene Server website.

This test was developed and its performance characteristics determined by the Department of Laboratory Medicine at the University of Washington.

Reference Range

See individual components

Ref. Range Notes

No mutation detected.

References

• Origa R. Beta-Thalassemia. GeneReviews: Adam MP, Ardinger HH, Pagon RA, Wallace SE, Bean LJH, Stephens K, Amemiya A, editors. 2000 Sep 28 [updated 2018 Jan 25]. 20301599
• Old JM. Screening and genetic diagnosis of haemoglobin disorders. Blood Rev 2003, 17:43-53. 12490210
• Globin Gene Server

Ordering & Collection

Specimen Type

Blood/Cultured amniocytes or chorionic villus cells/Extracted DNA from approved sample types (blood, chorionic villi, amniocyte). Direct chorionic villi, amniocyte, or amniotic fluid testing require Genetics Director approval. Please call the lab at 206-598-7021

Collection

Acceptable:

1. Whole blood:5 mL lavender top (EDTA) tube or yellow (ACD) top tube or 2 mL microtainer lavender top tube
   
   
2. Extracted DNA from blood, chorionic villi, and amniocytes: 500 ng (concentration >10 ng/uL)
   
   
3. Cultured amniocytes/chorionic villi: MCC is required for testing fetal samples. See MCC OLTG.
   
   
4. Also acceptable, but requires the Genetics Director's approval and a backup culture. Direct chorionic villi and/or TISSUE: Send 20mg of tissue in a sterile tube or RPMI culture media
   
   *NOTE: If a fetal sample (cultured amniocytes or chorionic villi) was received, add MCC to the order. Prenatal testing requires concomitant testing for maternal cell contamination (see Online Test Guide, MCC for ordering and specimen requirements). See Special Instructions.

Unacceptable: Heparin green top tubes, buccal swab

Forms & Requisitions

Genetics Requisition

Handling Instructions

SPS specimen handling:

1. Whole blood sample: store in the refrigerator
   
   
2. Cultured amniocytes/chorionic villi: store at room temperature. Call the Genetics lab upon receipt (206)598-7021.
   
   
3. Extracted DNA: store in the refrigerator

Quantity

Requested: Entire specimen
Minimum: Blood: 1 mL. If volume is less than 1mL, do not cancel. Send to Genetics lab. Confluent cultured cells: One (1) T25 flask. Extracted DNA: 250 ng

Processing

Receiving Instructions

If fetal tissue (cultured amniocytes or chorionic villi) was received for prenatal testing, consultation with the laboratory is required. Please notify the Genetics lab about prenatal studies via email at geneticshelp@uw.edu or call 206-598-7021.

For clients outside of UW, please include the most recent CBC and Hb electrophoresis result/s (if available), and/or any relevant clinical history.

Misc Sendout

Performance

Lab Department

Genetics(GEN)

Frequency

Performed weekly. Results within 2-3 weeks.

Available STAT?

No

Performing Location(s)

UW-MT	Genetics Attention: Genetics Lab Clinical lab, Room NW220 University of Washington Medical Center 1959 NE Pacific Street Seattle, WA 98195 Tel: 206-598–6429 M–F (7:30 AM–4:00 PM) Fax: 206-616-4584 Lab email: cgateam@uw.edu Tel (EXOME only): 206-543-0459	Faculty Jillian Buchan, PhD, FACMG Runjun Kumar, MD, PhD Regina Kwon, MD, MPH Christina Lockwood, PhD, DABCC, DABMGG Abbye McEwen, MD, PhD Colin Pritchard, MD, PhD Vera Paulson, MD, PhD Eric Konnick, MD, MS He Fang, PhD

Billing & Coding

CPT Codes

81364

LOINC

21689-5

Interfaced Order Code

UOW2171

Billing Comments

For pricing information, contact Client Support Services 206-520-4600 or 800-713-5198.