Test Code LAB3165 Hexosaminidase Levels A+B
Clinical System Name
Hexosaminidase Levels A + B
Synonyms
I Cell Disease
Tay Sachs
Sandhoffs
GM2 gangliosidosis
HEX AB Ta
Sample Requirements
Specimen: Whole Blood
Container(s): Dark Green/Sodium Heparin tube, Yellow/ACD A or B, Serum from Gold SST or Red top tubes
Preferred Vol: 2.0 mL
Minimum Vol: 1.0 mL
Processing Instructions
Reject due to:
Spin: Y
Aliquot:Y
Temp:-20 C
Storage location: Biochemical Genetics Box -20 C
Specimen should be spun and aliquoted within 2 hours of collection.
Off-site collection: Transport to Laboratory immediately.
Stability
Specimen Type | Temperature | Time |
---|---|---|
Aliquoted Serum/Plasma | Refrigerated |
7 days |
Freezer (-20 C)-preferred | 1 month |
Availability
STAT | Performed | TAT |
---|---|---|
N | Weekly | 7 days |
Contact the Biochemical Genetics Lab for requests outside of stated availability (206)987-2216.
Performing Laboratory
Seattle Children's Laboratory
Department
Department: Biochemical Genetics
Phone Number: 206-987-2216
CPT Codes
83080
Methodology
Method: Enzymatic/Fluorometric; 4-methylumbelliferyl substrate with heat inactivation
Analytical Volume:
Limitations:
Reference Range
Specimen Type | Normal Range <1 yr | Normal Range > 1 yr |
Total hexosaminidase (serum) |
1080-4400 | 600-1844 nmol/hr/mL |
% Hex A | 42-73% | 42-73% |
Carrier testing not performed
Description
Enzyme analysis of total hexosaminidase and % hexosaminidase A for diagnosis of GM 2 gangliosidosis (Tay-Sachs, Sandhoff) and evaluation of I-Cell disease.
Clinical Utility
Hexosaminidase A deficiency results in a group of
neurodegenerative disorders caused by the accumulation of a
cellular lipid called GM 2 ganglioside. This glycosphingolipid
accumulates in the lysosomes causing progressive weakness,
neurological deterioration, seizures, loss of milestones and loss
of vision.
The disorders range from acute infantile onset (classic Tay
Sachs disease) to juvenile, chronic and adult-onset forms. The
diagnosis of hexosaminidase A deficiency is characterized by absent
or profoundly deficient beta-hexosaminidase A activity in the
presence of normal beta-hexosaminidase B activity.
Patients with I Cell disease (mucolipidosis type I or II) have extreme elevation of serum/plasma total hexosaminidase.
Carrier testing by enzyme analysis is not available.
Requisition
Biochemical Genetics Requisition
On the requisition include clinical information needed for appropriate interpretation. (Age, gender, drug therapy and family history)
Special Instructions
Links to:
Consent Forms
Algorithms