Hexosaminidase A and Total, Leukocytes/Molecular Reflex

Abbrev Code:MMMISC   
Order Code:LAB4909Order Name:Hexo A Total Leuk Molec Reflex
Synonyms:Beta-N-Acetylglucosaminidase; Sandhoff Disease Carrier Screening; Tay Sachs Disease
Methodology:NAGR: Heat inactivation, fluorometric, semiautomated
CPT Codes: 83080 x2, 83080 x2, 81406 x1, 81479 x1
Turnaround Time:Specimens are sent to reference laboratory Mon-Thur only and not the day before a holiday; results are reported within 4-8 days.
Special Instructions:A signed copy of a genetic consent form should be in the patient's chart. See Associated Links.

This test was developed and its performance characteristics determined by Laboratory Medicine and Pathology, Mayo Clinic. This test has not been cleared by the U.S. Food and Drug Administration.

Associated Links:

Genetic Testing Consent Form

Collection Instructions

Specimen:Whole Blood
Optimal Volume:6 mL
Minimum\Peds Volume:5 mL
Container:Yellow (ACD, Solution A) tube available from laboratory

Processing and Shipping

Specimen Processing:Whole blood. Do not centrifuge. Ship within 24 hours of collection in the original container.
Shipping Instructions:Ship same day at refrigerated temperature; do not freeze. Must arrive Mon-Fri only. Specimens must arrive at the reference laboratory within 96 hours after collection.
Stability:Ship same day in original container.
Test Performed at or Referral Lab Lab Sendouts  (Mayo)
Referral Lab number:NAGR


Reference Range:

Hexosaminidase, Total

≤15 y

≥20 nmol/min/mg

≥16 y

16.4-36.2 nmol/min/mg


Hexosaminidase, Percent A

≤15 y

20-80% of total

≥16 y

63-75% of total




Hex A usually makes up >62% of the total hexosaminidase activity in leukocytes (normal = 63%-75% Hex A). The key factor for determining whether an individual is a carrier of, or affected with, Tay-Sachs disease is the percent Hex A in leukocytes:


63-75% Hex A

Normal (noncarrier)

58-62% Hex A

Ambiguous (molecular testing performed to discern carriers from noncarriers and to provide the most options for prenatal diagnosis).

Less than 58% Hex A

Carrier status (molecular testing performed to provide the most options for prenatal diagnosis.)

Less than 20% Hex A




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