Testing for Tay-Sachs Disease and Sandhoff Disease
The following tests are available for diagnostic and carrier testing for Tay-Sachs and Sandhoff diseases.
NAGR / Hexosaminidase A and Total, Leukocytes/Molecular Reflex:
-This is the recommended test for carrier testing for Tay-Sachs disease.
-Testing begins with hexosaminidase A and total enzyme analysis. If the results are consistent with an affected or carrier individual, Tay-Sachs mutation analysis will automatically be performed on the original specimen.
-This is not the recommended test for Sandhoff disease; however, if the results are suggestive of Sandhoff disease or carrier status, this will be indicated in the interpretive comment along with recommendations for additional testing. Follow-up testing for Sandhoff must be ordered separately.
-This test is appropriate for males and pregnant or nonpregnant females.
NAGW / Hexosaminidase A and Total Hexosaminidase, Leukocytes:
-This test can be used for diagnosis and carrier testing for Tay-Sachs disease or Sandhoff disease.
-Results for hexosaminidase A and total enzyme analysis are reported with recommendations for additional testing when appropriate. All follow-up testing must be ordered separately on new specimens.
-This test is appropriate for males and pregnant or nonpregnant females.
NAGS / Hexosaminidase A and Total Hexosaminidase, Serum:
-This is the recommended test for diagnosis and carrier testing for Sandhoff disease. This test also can be used for diagnosis and carrier testing for Tay-Sachs disease.
-Results for hexosaminidase A and total enzyme analysis are reported with recommendations for additional testing when appropriate.
-If results indicate normal, indeterminate, or carrier status and the suspicion of Tay-Sachs disease (TSD) remains high, MUGS / Hexosaminidase A (MUGS), Serum for TSD-B1 variant can typically be added and performed on the same specimen.
-With the exception of MUGS, all follow-up testing must be ordered separately on new specimens.
-This test is not appropriate for pregnant females. This test is appropriate for males and nonpregnant females.
-Although a leukocyte test is preferred for Tay-Sachs disease, this test can be used if it is difficult to obtain enough blood to perform testing, as may be the case with infants. Additionally, the biochemical workup for TSD could be completed with MUGS testing without collecting a new specimen.
MUGS / Hexosaminidase A (MUGS), Serum:
-This is the recommended test for diagnosis and carrier testing for the B1 variant of Tay-Sachs disease. This test will not detect Sandhoff disease.
-This test is performed on serum using the natural substrate. It should not be ordered as a first-line test. Rather, this test should be ordered when the NAGR, NAGW, NAGS indicate normal, indeterminate, or carrier results and the suspicion of Tay-Sachs disease remains high. In most cases, this test can be performed on the original specimen collected for NAGS.
