Test Overview

Test Methodology

Heat Inactivation, Fluorometric, Automated

Test Usage

Preferred test to order for Tay-Sachs disease, carriers of Tay Sachs, Sandhoff's disease, and carriers of Sandhoff's.

Reference Range*

HEXOSAMINIDASE TOTAL, LEUKOCYTES: <=15 yrs: >=20 nmol/min/mg, >=16 yrs: 16.4 - 36.2 nmol/min/mg; HEXOSAMINIDASE PERCENT A, LEUKOCYTES: <=15 yrs: 20 - 80% of total, >=16 yrs: 63 - 75% of total; HEXOSAMINIDASE TOTAL, SERUM: <=15 yrs: >=20 nmol/min/mL, >=16 yrs: 10.4 - 23.8 nmol/min/mL; HEXOSAMINIDASE PERCENT A, SERUM: <=15 yrs: 20 - 90% of total, >=16 yrs: 56 - 80% of total.

* Reference ranges may change over time. Please refer to the original patient report when evaluating results.

Test Limitations

Total hexosaminidase is increased in pregnancy due to the significant appearance of a third heat-stable enzyme. Serum results are ambiguous on pregnant females and will not be run.

Test Details

Days Test Performed

Monday, Wednesday, Friday

Analytic Time

2 - 5 days

Soft Order Code

NAGW

MiChart Code

Hexosaminidase A, Total, Leukocytes

Laboratory

Sendout

Laboratory Reference

Mayo NAGS (8774) Serum, NAGR (82943) Leukocytes with Molecular Reflex, NAGW (8775) Leukocytes

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Specimen Requirements

Offsite Collection Instructions

MALES (serum): Collect specimen in a red top tube from a fasting patient. Centrifuge, aliquot serum into a plastic vial and freeze (do not refreeze thawed serum). FEMALES (leukocytes): Collect blood in 7 mL yellow top tube (ACD) solution A or B from a fasting patient. Refrigerate intact ACD tube (frozen ACD tube is unacceptable). ACD specimen must arrive within 48 hours of collection.

Special Handing

Fasting specimen.

Contraindication

Hexosaminase A and Total, Serum (NAGS), is contraindicated in pregnant females. During pregnancy the total hexosaminidase in serum is increased and the percentage of hexosaminidase A appears to be decreased, resulting in a false positive carrier result. In leukocytes, pregnancy does not elevate total hexosaminidase, therefore leukocyte hexosaminidase testing is recommended during pregnancy.

Container

Red Top Tube

Normal Volume

Serum: 1 mL serum; Leukocytes: 7.0 mL ACD (solution A or B) whole blood

Minimum Volume

Serum: 0.5 mL serum; Leukocytes: 5.0 mL ACD (solution A or B) whole blood

Additional Information

The preferred test for both pregnant and non-pregnant females is Hexosaminase A and Total, Leukocytes with Molecular Reflex (NAGR). If females wish screening for carrier status of hexosaminidase A deficiency, they must be tested prior to pregnancy. If the female is pregnant, we strongly suggest that her mate be tested for carrier status. Positive (or ambiguous) findings in the mate indicate a second order test on the female with leukocyte preparations. Please specify Hexosaminase A and Total, Leukocytes with Molecular Reflex (NAGR), Hexosaminase A and Total, Serum (NAGS), or Hexosaminidase A and Total, Leukocytes (NAGW). Leukocytes with Molecular Reflex assay includes leukocyte testing; if these results are abnormal (<63% Hexosaminidase A), Tay-Sachs Disease Mutation Analysis (Mayo TSD) will be performed at an additional charge. By ordering this test the clinician acknowledges that additional reflex testing will be performed and billed at a separate additional charge if indicated. Test sent to Mayo Medical Laboratories.

Billing Information

Fee Codes


CPT Code

83080 per specimen

Reflex Fee Code

22003 TSD

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