Alpha Hemoglobin DNA Sequence

DNA sequencing of the coding regions and introns of both the alpha1 (HBA1) and alpha 2 globin (HBA2) genes in both directions to detect point mutations causing alpha globin variants and some types of alpha thalassemia.

This test detects alpha globin variants and non-deletional alpha thalassemia mutations (e.g. Hb Constant Spring). The coding regions and introns of both HBA1 and HBA2 genes are sequenced in bidirectionally. The reference mRNA sequences are HBA1 (NM_000558.3) and HBA2 (NM_000517.4) with nucleotide 1 corresponding to the A of the AUG initiation codon (nucleotide 38 of both reference sequences) and codon 1 corresponding to the valine encoded by GTG (nucleotides 41-43 of both reference sequences). The sensitivity of this test for detecting nucleotide substitutions, small insertions and deletions and in the alpha 1 (HBA1) and alpha 2 (HBA2) genes is theoretically >98%. This test will not detect mutations that lie outside of the sequenced regions, nor large HBA1 and HBA2 gene deletions (e.g. –a3.7, – –SEA). This test was developed and its performance characteristics determined by the Department of Laboratory Medicine at the University of Washington.

BLOOD:

• Adult: 5 mL LAVENDER TOP tube
• Child: 2 mL LAVENDER TOP tube
• Also acceptable: YELLOW TOP (ACD) tube
• Unacceptable: Heparin green top tubes

AMNIOCYTES or CULTURED CHORIONIC VILLUS CELLS:

• Two (2) T23 or One (1) T75 flask (minimum 1-T25 flask)

CHORIONIC VILLIS and/or TISSUE:

• In sterile tube or culture media, at least 5 mg tissue.

Prenatal testing requires concomitant testing for maternal cell contamination (see Online Test Guide, Lab Mnemonic Maternal Cell Contamination [MCC] for ordering and specimen requirements)

Blood: Refrigerate whole blood up to 1 week.

Amniocytes & cultured CVS cells: hold flasks at room temperature.

Chorionic villi &/or tissue: hold at room temperature.

Outside Laboratories: Ship whole blood at ambient temperature for receipt within 1 week of specimen collection. - For cultured amniocytes or chorionic villus cells and for CVS or other tissue, transport and store at room temperature within 24 hours of obtaining CV or removing cultured cells from incubator.