Alpha Globin Test

Alpha globin tests are genetic assays that detect deletions or mutations in the HBA1 and HBA2 genes on chromosome 16 to diagnose alpha thalassemia or carrier status. These tests confirm abnormalities linked to microcytic anaemia, family history, or prenatal risks by analysing blood or fetal samples.

Common Test Types

1. Deletion Analysis (First-Tier): Targets frequent deletions like alpha-3.7, alpha-4.2, SEA, FIL, THAI, and MED using PCR and gel electrophoresis; detects ~95% of cases.
   
2. Gene Sequencing (Second-Tier): PCR/Sanger sequencing identifies non-deletional variants (e.g., Hb Constant Spring) after negative deletion tests or abnormal electrophoresis.

When to Test?

Indications include microcytic anaemia investigation, carrier screening in high-risk ethnic groups (Southeast Asian, African, Mediterranean), reproductive risk assessment, or prenatal diagnosis via amniocytes/chorionic villi.

Specimen and Process

• Whole blood (EDTA tube, 1-5 mL) is standard; extracted DNA or fetal samples also accepted.
• Prior hemoglobin electrophoresis aids interpretation.
• Alpha globin gene tests in India are usually done as an “Alpha Thalassemia Mutation Detection” or “Alpha Globin Gene Analysis” test.

Note: Basic PCR test for common deletions, full gene sequencing or NGS panels cost more.