When diagnosing Tay-Sachs, the doctor will ask questions about symptoms and family history, perform a physical exam, and recommend certain tests, including a blood test.
This blood test measures beta-hexosaminidase A activity to identify patients and carriers of Tay-Sachs disease. It looks for specific mutations or changes in the gene that codes for HEXA.
Since 1985, when the HEXA gene was isolated, over 50 different mutations in this gene have been identified. However, some mutations are still unknown. The current tests used when diagnosing Tay-Sachs disease detect about 95 percent of carriers of Ashkenazi Jewish background and about 60 percent of carriers in the general population.