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HelpTest Code SXDBS Sorbitol and Xylitol, Quantitative, Blood Spot
Ordering Guidance
This is a test for diagnosis and treatment monitoring for sorbitol dehydrogenase (SORD) deficiency-related peripheral neuropathy.
Necessary Information
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
Fasting: 8 hours, required. Infants should not fast overnight; collect just before next feeding.
Supplies: Card-Blood Spot Collection (Filter Paper) (T493)
Container/Tube:
Preferred: Card-Blood Spot Collection (Filter Paper)
Acceptable: PerkinElmer 226 filter paper, Munktell filter paper, Whatman protein Saver 903 paper, local newborn screening card, or blood collected in tubes containing EDTA (preferred) or sodium heparin and dried on filter paper.
Specimen Volume: 2 Blood spots
Collection Instructions:
1. An alternative blood collection option for a patient older than 1 year is a fingerstick. For detailed instructions, see How to Collect a Dried Blood Spot Sample.
2. Completely fill at least 2 circles on the filter paper card (approximately 100 microliters blood per circle).
3. Let blood dry on filter paper at ambient temperature in a horizontal position for a minimum of 3 hours.
4. Do not expose specimen to heat or direct sunlight.
5. Do not stack wet specimens.
6. Keep specimen dry.
Additional Information:
1. For collection instructions, see Blood Spot Collection Instructions
2. For collection instructions in Spanish, see Blood Spot Collection Card-Spanish Instructions (T777)
3. For collection instructions in Chinese, see Blood Spot Collection Card-Chinese Instructions (T800)
Forms
Secondary ID
623688Useful For
Screening and treatment monitoring for sorbitol dehydrogenase deficiency-related neuropathy
Genetics Test Information
This test is used to aid in the diagnosis and treatment monitoring of patients with sorbitol dehydrogenase-related peripheral neuropathy.
Method Name
Gas Chromatography Mass Spectrometry (GC-MS) Stable Isotope Dilution Analysis
Reporting Name
Sorbitol and Xylitol, Quant, DBSSpecimen Type
Blood SpotSpecimen Minimum Volume
1 Blood spot
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Blood Spot | Ambient (preferred) | 31 days | FILTER PAPER |
| Frozen | 90 days | FILTER PAPER | |
| Refrigerated | 90 days | FILTER PAPER |
Reject Due To
| Blood spot specimen that shows serum rings or has multiple layers | Reject |
| Insufficient specimen | Reject |
| Non-approved filter papers | Reject |
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 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, two urine polyols, sorbitol and xylitol, are elevated in both blood and urine when compared to controls. Polyols are sugar alcohols that have been identified in blood, urine, and cerebrospinal fluid. Abnormal blood and urine (SORD / Sorbitol and Xylitol, Quantitative, Random, Urine) polyol results 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: ≤30.0 nmol/mL
Xylitol: ≤10.0 nmol/mL
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 may be required to identify both causative variants.
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;30(7):2001-2011. doi:10.1111/ene.15793
4. Zhu Y, Lobato AG, Rebelo AP, et al. Sorbitol reduction via govorestat ameliorates synaptic dysfunction and neurodegeneration in sorbitol dehydrogenase deficiency. JCI Insight. 2023;8(10):e164954. doi:10.1172/jci.insight.164954
Method Description
Blood spot specimens are spiked with a mixture of labeled internal standards and evaporated. The dry residue is derivatized to form trimethylsilyl ethers, then extracted with hexane. Specimens are analyzed by gas chromatography mass spectrometry (GC/MS) selected ion monitoring using positive ammonia chemical ionization and stable isotope dilution.(Unpublished Mayo method)
Day(s) Performed
Friday
Report Available
5 to 11 daysSpecimen Retention Time
Normal result: 1 month; Abnormal result: IndefinitelyPerforming 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 |
|---|---|---|
| SXDBS | Sorbitol and Xylitol, Quant, DBS | In Process |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| 623692 | Interpretation | 59462-2 |
| 623690 | Sorbitol | In Process |
| 623691 | Xylitol | In Process |
| 623693 | Reviewed By | 18771-6 |