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HelpTest Code SORD Sorbitol and Xylitol, Quantitative, Random, Urine
Ordering Guidance
This is the preferred test for assessing sorbitol dehydrogenase (SORD) deficiency-related peripheral neuropathy. The preferred test for monitoring effectiveness of treatment in patients with phosphomannomutase 2 deficiency (PMM2-CDG) is SORBU / Sorbitol and Mannitol, Quantitative, Random, Urine
Necessary Information
1. Patient’s age is required.
2. Biochemical Genetics Patient Information (T602) is recommended, but not required, to be filled out and sent with the specimen to aid in the interpretation of test results.
Specimen Required
Supplies: Urine Tubes, 10mL (T068)
Container/Tube: Plastic, 10-mL urine tube
Specimen Volume: 2 mL
Collection Instructions:
1. Collect a random urine specimen.
2. No preservative needed.
Forms
1. Biochemical Genetics Patient Information (T602) is recommended, but not required, to be filled out and sent with the specimen to aid in the interpretation of test results.
2 If not ordering electronically, complete, print, and send 1 of the following forms with the specimen:
Secondary ID
620920Useful For
Screening for sorbitol dehydrogenase deficiency-related neuropathy
Method Name
Gas Chromatography Mass Spectrometry (GC-MS)
Reporting Name
Sorbitol and Xylitol, QN, USpecimen Type
UrineSpecimen Minimum Volume
1 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Urine | Refrigerated (preferred) | 28 days | |
| Frozen | 28 days |
Reject Due To
All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.Clinical Information
Sorbitol dehydrogenase (SORD) deficiency is an autosomal recessive condition caused by biallelic variants in the SORD gene resulting in peripheral neuropathy, which may present as clinically similar to Charcot-Marie-Tooth disease type 2 or distal hereditary motor neuropathy. The SORD enzyme catalyzes the breakdown of sorbitol to fructose. In patients with SORD deficiency-related peripheral neuropathy, the urine polyols, sorbitol and xylitol, are elevated when compared to controls. Polyols are sugar alcohols that have been identified in blood, urine, and cerebrospinal fluid. An abnormal urine polyol result suggestive of SORD deficiency-related peripheral neuropathy should be confirmed with molecular genetic analysis. For molecular confirmation, genetic testing for SORD can be performed (CGPH / Custom Gene Panel, Hereditary, Next-Generation Sequencing, Varies; specify gene list ID: NEUROLOGY-S3NL4H).
Reference Values
Sorbitol:
<35 mmol/mol creatinine
Xylitol:
<351 mmol/mol creatinine
Interpretation
An interpretive report will be provided.
All profiles are reviewed by the laboratory director and interpretation is based on pattern recognition. A detailed interpretation is given, including an overview of the results and of their significance, a correlation to available clinical information, and recommendations for in vitro confirmatory studies (molecular analysis).
Cautions
A positive test result is diagnostic of sorbitol dehydrogenase (SORD) deficiency-related neuropathy; however, it is strongly recommended to follow-up with molecular analysis. Molecular analysis of the SORD gene is complicated by the SORD2P pseudogene and specific molecular testing approaches maybe required.
Clinical Reference
1. Cortese A, Zhu Y, Rebelo AP, et al. Biallelic mutations in SORD cause a common and potentially treatable hereditary neuropathy with implications for diabetes. Nat Genet 2020;52(5):473-481. doi:10.1038/s41588-020-0615-4
2. Lassuthova P, Mazanec R, Stanek D, et al. Biallelic variants in the SORD gene are one of the most common causes of hereditary neuropathy among Czech patients. Sci Rep 2021;11(1):8443. doi:10.1038/s41598-021-86857-0
3. Pons N, Fernandez-Eulate G, Pegat A, et al. SORD-related peripheral neuropathy in a French and Swiss cohort: Clinical features, genetic analyses, and sorbitol dosages. Eur J Neurol 2023. doi:10.1111/ene.15793
Method Description
A total of 200 mcL of urine is spiked with a mixture of labeled internal standards, allowed to equilibrate, and evaporated. The dry residue is derivatized to form trimethylsilyl esters, then extracted with hexane. Specimens are analyzed by gas chromatography mass spectrometry, selected ion monitoring using ammonia chemical ionization and a stable isotope dilution method.(Jansen G, Muskiet F, Schierbeek H, Berger R, van der Slik W. Capillary gas chromatography profiling of urinary, plasma, and erythrocyte sugars and polyols as their trimethylsilyl derivatives, preceded by a simple and rapid prepurification method. Clin Chim Acta. 1986; 157[3]:277-294; Marolt G, Kolar M. Analytical methods for determination of phytic acid and other inositol phosphates: A review. Molecules. 2020;26[1]:174)
Day(s) Performed
Tuesday, Friday
Report Available
3 to 7 daysSpecimen Retention Time
3 monthsPerforming Laboratory
Mayo Clinic Laboratories in Rochester
Test Classification
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.CPT Code Information
82542
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| SORD | Sorbitol and Xylitol, QN, U | 74447-4 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| 620921 | Interpretation | 59462-2 |
| 620922 | Sorbitol | 48152-3 |
| 620923 | Xylitol | 48132-5 |
| 620927 | Reviewed By | 18771-6 |