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HelpOrder Code LABNAGR Hexosaminidase A and Total, Leukocytes/Molecular Reflex, Whole Blood
Additional Codes
Mayo Test Code: NAGR
Reporting Name
Hexosaminidase A and Tot, WBC/MoleUseful For
Carrier detection and diagnosis of Tay-Sachs disease
Carrier detection and diagnosis of Sandhoff disease
Testing Algorithm
If result interpretation is consistent with carrier, indeterminate, or affected for Tay-Sachs disease or Sandhoff disease, then next-generation sequencing to detect single nucleotide and copy number variants for HEXA or HEXB, respectively, will be performed at an additional charge.
For more information see Tay-Sachs and Related Disorders Diagnostic Testing Algorithm
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Specimen Type
Whole Blood ACDOrdering Guidance
The following tests are available for diagnostic and carrier testing for Tay-Sachs and Sandhoff diseases.
NAGR / Hexosaminidase A and Total, Leukocytes/Molecular Reflex, Whole Blood:
-This is the recommended test for carrier testing for Tay-Sachs disease and Sandhoff disease.
-Testing begins with hexosaminidase A and total enzyme analysis. If the results are consistent with an affected or carrier for Tay-Sachs disease or Sandhoff disease, next generation sequencing to detect single nucleotide and copy number variants for HEXA or HEXB, respectively, will automatically be performed on the original specimen.
-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 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.
-If results indicate normal, indeterminate, or carrier status and the suspicion of Tay-Sachs disease remains high, MUGS / Hexosaminidase A, Serum for Tay-Sachs disease (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 or women receiving hormonal contraception. This test is appropriate for males and nonpregnant females.
-This test is particularly useful when it is difficult to obtain enough blood to perform leukocyte testing (NAGR or NAGW), as may be the case with infants.
MUGS / Hexosaminidase A, 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 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.
Shipping Instructions
For optimal isolation of leukocytes, it is recommended the specimen arrive refrigerated within 6 days of collection to be stabilized. Collect specimen Monday through Thursday only and not the day before a holiday. Specimen should be collected and packaged as close to shipping time as possible.
Specimen Required
Container/Tube:
Preferred: Yellow top (ACD solution B)
Acceptable: Yellow top (ACD solution A)
Specimen Volume: 6 mL
Collection Instructions: Send whole blood specimen in original tube. Do not aliquot.
Specimen Minimum Volume
5 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Whole Blood ACD | Refrigerated (preferred) | 6 days | YELLOW TOP/ACD |
| Ambient | 6 days | YELLOW TOP/ACD |
Special Instructions
Reference Values
HEXOSAMINIDASE TOTAL
≤15 years: ≥20 nmol/min/mg
≥16 years: 16.4-36.2 nmol/min/mg
HEXOSAMINIDASE PERCENT A
≤15 years: 20-80% of total
≥16 years: 63-75% of total
Day(s) Performed
Preanalytical processing occurs Monday through Saturday.
Assay is performed: Friday
CPT Code Information
83080 x2
81406 (if appropriate)
81479 (if appropriate)
Method Description
Leukocyte hexosaminidase A and total hexosaminidase are estimated using a semiautomated modification of the method of O'Brien, et al (1970) with further specific recommendations on specimen preparation as outlined by the International Tay-Sachs Disease Testing Quality Control and Data Collection Center.(O'Brien JS, Okada S, Chen A, Fillerup DL: Tay-Sachs disease: detection of heterozygotes and homozygotes by hexosaminidase assay. N Engl J Med. 1970;283[1]:15-20; Cowan T, Pasquali M: Laboratory investigations of inborn errors of metabolism. In: Sarafoglou K, Hoffman GF, Roth KS, eds. Pediatric Endocrinology and Inborn Errors of Metabolism. 2nd ed. McGraw-Hill; 2017:1139-1158)
Next-generation sequencing (NGS) and/or Sanger sequencing are performed to test for the presence of variants in coding regions and intron/exon boundaries of the gene analyzed, as well as some other regions that have known disease-causing variants. The human genome reference GRCh37/hg19 build was used for sequence read alignment. At least 99% of the bases are covered at a read depth over 30X. Sensitivity is estimated at above 99% for single nucleotide variants, above 94% for deletion-insertions (delins) less than 40 base pairs (bp), above 95% for deletions up to 75 bp and insertions up to 47 bp. NGS and/or a polymerase chain reaction based quantitative method is performed to test for the presence of deletions and duplications in the gene analyzed.
There may be regions of genes that cannot be effectively evaluated by sequencing or deletion and duplication analysis as a result of technical limitations of the assay, including regions of homology, high guanine-cytosine (GC) content, and repetitive sequences. Confirmation of select reportable variants may be performed by alternate methodologies based on internal laboratory criteria.(Unpublished Mayo method)
Reject Due To
| Gross hemolysis | Reject |
Method Name
Heat Inactivation/Fluorometric/Semiautomated
Forms
1. New York Clients-Informed consent is required. Document on the request form or electronic order that a copy is on file. The following documents are available:
-Informed Consent for Genetic Testing (T576)
-Informed Consent for Genetic Testing-Spanish (T826)
2. Biochemical Genetics Patient Information (T602)
3. If not ordering electronically, complete, print, and send a Biochemical Genetics Test Request (T798) with the specimen.
Reflex Tests
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| CGPH | Custom Gene Panel, Hereditary | Yes | No |
| HEXBZ | HEXB Gene, Full Gene Analysis | Yes | No |